Udi Dahan   Udi Dahan – The Software Simplist
Enterprise Development Expert & SOA Specialist
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[Ask Udi] Two services operating on the same entity

Friday, February 19th, 2016

last_pieceMost of my regular readers know that I recommend against having more than one service operating on the same entity, but with the groundswell of interest around microservices, there appear to be more and more people who are falling into this trap, so I thought it worthwhile to do a short refresher on the topic.

I got this question submitted the other day on an old post from 2007 on autonomous services and enterprise entity aggregation:

What happens when two services must be able to create/update the same entities?

For example, take this scenario, lets suppose we have two services: Marketing Service and Product Inventory Service. Marketing Service must be able to create new instances of the business entity Products, as the marketing team needs to make publicity about new products before the products is available for sale. On the other hand, the marketing department will not make publicity for the all products, so the Product Inventory Service needs to be able to create new instances of the Product too.

How to implement autonomous services when there is more than one service which is authoritative services over the same business entity?

Where confusion starts

When people look to allocate responsibility to their services, there are a number of implicit assumptions that are often made that make it difficult to follow the rules of service design.

Problematic Assumption #1

Services should be aligned with organizational boundaries.

For the full story as to why this isn’t a good idea, read my post on people, politics, and the single responsibility principle.

In the question above, assuming that the Marketing Service does all the things that the Marketing Department does, and inversely doesn’t do the things the department doesn’t do gets us into trouble. If a service is responsible for the creation of an entity, there shouldn’t be any other service that can create that entity. So, in this case, the “Marketing Service” (assuming that that would still be the best name for it) would always create the “Product” entity – assuming that that is the right name and set of attributes to put together.

Problematic Assumption #2

Entities should represent “real world” things.

For the full story as to why this isn’t a good idea, read my post don’t try to model the real world, it doesn’t exist.

In the question above, assuming that there is an entity called Product and that entity owns all data about a product like its’ name, price, and amount in inventory gets us into trouble. You see, each of those attributes relates to very different business processes when we look at their use in transactional logic. I mean, sure, you may need to show all the data on one screen in the UI, but that can be done fairly simply using UI composition techniques. For some more advanced UI composition ideas, see the video in this post on service-oriented composition.

Anyway, instead of having a single Product entity, we could have a “CatalogItem” entity that would encompass information about the “product” like its name, description, image, and category information. That entity would share a common ID with entities owned by other services – like an “InventoryItem” that would own information like the quantity of the product.

Depending on other more detailed information about the domain, we may decide on whether data like the dimensions and weight of the product would go together with the quantity or on a separate “ShippableItem” entity owned by yet a different service. One justification for the separation is that the quantity of inventory is quite a bit more volatile than the dimensions and weight. Still, we could have separate entities for those things in the same service.

And that’s why it’s so difficult

When you can no longer rely on the crutches of organizational structure and the nouns of the domain, it becomes much harder to model your domain – dividing up responsibility into services and setting up the right entity model for each of them. At that point, you really need to dive deep into the domain and analyze the way each attribute of data is used and what kind of transactional integrity constraints are real and which are imagined.

For those of you who haven’t gone back and read all of my older posts (and let’s be honest, nobody does that when they subscribe to a blog), I hope the links above give you some next steps to take in learning about service design.

If you want even more

I’ve been teaching about this stuff for a while now and most of the people who’ve attended the training think it’s quite helpful. To get a sense of what this course is like, check out this short video

The thing is that these courses fill up pretty quick – the upcoming ones in Dallas Texas in March and London UK in April have already sold out, so I’m going to try to do more this year than just the four I did last year.

The next one that is now open for registration will be in Sydney Australia in May.

I’m going to try and see if I can get back to the US in August and London in December, but for now the next other course that is already available will be in Denver CO in November.

For those of you who would have a hard time traveling or taking time off work, you can get access to the recording of the first two days of the course – totally free.

More questions?

Feel free to leave a comment and I’ll do my best to help you out.

NSBCon 2015 – Dallas Texas

Friday, October 30th, 2015


Seeing as it’s been just about a year since the last NSBCon we ran in New York City, I’m happy to say we’re bringing NSBCon back to the US – this time in Dallas Texas, Dec 1-4.

Click here for the full details.

First – the war stories

For those of you who have been wondering about what it would be like to apply the Service-Oriented principles I blog about, we’ll hear the war story of one brave architect’s journey down that path, which kinds of messaging patterns helped, and which it didn’t.

Another point of concern for people considering event-driven approaches to building systems is how to keep control of all of these loosely-coupled bits and pieces. Luckily we’ll have a session talking about various monitoring and devops techniques to keep on top of everything that’s happening – and not just a theory of how that could be done, but a “from the trenches” account of how well they actually worked.

Then – down to the metal

In addition to some really “down and dirty” sessions about all the cool nifty NServiceBus features that have come out this past year, we’ll also give you a sneak peek into what’s coming in the future (after keeping very tight lipped about our future roadmap).

And finally, we’ll talk a bit about the actor model and Akka.net – where they fit in message-driven architectures and how to get the two worlds to play together nicely.

And finally – an unconference

When all is said and done, what you really want is some time to talk through your specific challenges with people who’ve “been there” and “done that”. That’s why our last day is a full interactive “unconference” meaning that you get to set the agenda, get direct access to all the speakers, and even grab some NServiceBus experts to debug some code with you.

If you’ve never been to an unconference before, you don’t know what you’re missing.

So, hurry up!

Discounted “early bird” tickets are almost sold out.

I really hope to see you all there.

Check it out.

Training still happening

Monday, September 21st, 2015

So, about 2.5 years ago I wrote that I would be winding down my training, specifically saying “In any case, I’ll be giving the course 4 more times, and that’ll be it.”

Well, that wasn’t it

Now, even though I did scale back the training quite a lot – from around 10 public courses a year down to 2, they didn’t stop entirely. After settling into what appears to be a new stable and sustainable rhythm, I’m experimenting with bringing the training up to 4 times a year / once a quarter. So far, so good.

Beyond a tweet here and there about those courses, I haven’t been blogging about them – or blogging much at all really (this will be my 3rd post this year).

Anyway, I’m getting back into the swing of things and there are some courses coming up:

Next up Sydney, then Dallas

The next one is in Sydney Australia Oct 12-16 – register here. Somewhat surprisingly, this is pretty close to selling out so if you’re down under, you’ll probably want to sign up for this one as I probably won’t be back for at least a year.

The one after that will be in Dallas TX, March 7-11 – register here. I know there were a lot of you in the US that wanted to go to the last one in Austin, but that one sold out pretty quick. Hopefully you’ll be able to get in this one – and there’s still plenty of time if you want to get the early-bird price.

Looking forwards

Other than the courses, you can find me (and a bunch of other people in Particular) speaking at various user groups and conferences around the world. Here’s the list of upcoming events. Come up and say hello 🙂

* Here’s a gist of some ugly javascript to get the source data for that.

In Closing

I really do enjoy teaching and seeing how people’s eyes light up when something all of sudden clicks for them. I’ll probably continue teaching, in one form or another, for quite some time.

Hope to see you at one of my next courses or events.

Microservices presentation [London 2014]

Tuesday, July 21st, 2015

… in which I realize I shouldn’t put off blogging about the presentations I’ve given.

This one is from µCon 2014: The Microservices Conference at Skills Matter in London.


The title of this talk was: An Integrated Services Approach

and the description:

After many years of the largely enterprise-scale SOA philosophy being applied across multiple systems, we’re now seeing some of that philosophy being applied to the design of the systems themselves with Microservices. Unfortunately, unless we integrate these enterprise and system level philosophies appropriately, we’ll end up with a mess of data duplication and coupling that may even result in businesses running on inconsistent data. Join Udi for a discussion of a unified approach that leverages the best of both worlds.

Hope you find it interesting.

Finding Service Boundaries – illustrated in healthcare

Monday, February 2nd, 2015

A couple of months back I gave a presentation at NDC London about how to find service boundaries, giving examples from the field of healthcare. The recording is now online here.

If you want to learn more about these topics, check out more of my posts on SOA here.

If you want the full, in-depth, zero-to-sixty experience – you should really attend my Advanced Distributed Systems Design course. The next one is in March in San Francisco but there will be others around the world through the rest of this year.

For the full list of events, click here.

Ask me anything – Dec 11

Monday, December 8th, 2014

This coming Thursday, Dec 11 I’m going to be doing an “Ask Me Anything”.

For those of you who aren’t familiar with the format, an “Ask Me Anything” (or AMA for short) is a kind of online “press conference” which was popularized on Reddit, and has had fairly well-known people do them including President Obama, Bill Gates, Madonna, and more. For more information, see Wikipedia on the topic.

Here’s how it works

First thing, sign up at http://particular.net/ask-udi-dahan-anything to get the conference info.

Then, check out and vote on the questions people have already asked, and ask your own.

Of course, you can also loop some friends in to vote for your questions, but I will do my best to answer as many questions as I can – live on Thursday Dec 11, at 12pm EST (5pm GMT).

Even if you can’t make that time, the recording will be available afterwards. Once I have the link for that, I’ll blog it as well.

But don’t just take a passive wait-and-see approach. If you’ve been reading my blog, I know you’ve got questions about SOA, DDD, CQRS, messaging, NoSQL databases, and more – so this is your chance to get them answered.

Go on then: Ask me anything. 🙂

Watch out for superficial invariants

Sunday, November 16th, 2014

As I was reading a blog post on CQRS, Aggregate Roots, and Invariants here, I became aware of a mistake I’ve seen many developers make over the years and I thought I’d call it out real quick.

Superficial Invariants

Taken from the blog post mentioned above: “For example, an employee cannot take more annual leave than they have.”

This falls into the trap of applying mathematical thinking (which we developers possess in great quantities) to the business world. The business world isn’t that mathematical (in general), and tends to have many more shades of gray expressed as “business rules” which can, and do, change.

Rules – not invariants

Employees can’t take more annual leave than they have.
… unless their manager approves.
… but that’s only up to 2 days.
… unless their manager is a VP, and then it’s up to 5 days.
… and that negative balance will be deducted from next year’s leave.
… Oh, and if the employee leaves the company before then, then the value of those negative days will be deducted from their final paycheck.

Impact on your domain

First of all, I hope you see that this isn’t something that you would trivially implement on an Employee object.

If you read these rules more carefully, you’ll probably notice that they’re speaking about a long-running process.

First, there is a request for leave. Then there’s an approval (with certain rules) which may come sometime later. And the approval itself may not even end the process – if the balance becomes negative.

And, as you’ve probably heard me say before, you end up with sagas as your aggregate roots (see Race conditions don’t exist from 4 years ago).

And a word about Bounded Contexts

Notice that these rules don’t care very much about things like the employee’s name, phone number, email, etc. Similarly, logic that deals with that data probably doesn’t care about the number of days of leave an employee takes.

In other words, these sets of data and logic can be said to belong to different Sub-Domains (in DDD terminology).

As such, it can make sense to take the annual leave logic and put it in a bounded context separate from the one responsible for the contact info.

In closing

In many of the samples and blog posts I see online, an overly simplified problem domain is implemented showing how the given implementation technique would be applied.

The problem is that developers then use that implementation technique as a “cookie cutter”, trying to fit real-world requirements into it, and then end up making a pretty big mess.

The more you delve into real-world requirements of business domains, the less you’ll see of mathematical invariants (unless, maybe, you’re building a physics engine for a game or something) and the more you’ll see long-running processes unfolding in front of you.

Regardless of whether you use NServiceBus sagas or not, start looking at the world as dynamic long-running processes rather than static noun-centric entities.

Best US Supermarket running NServiceBus (for years)

Tuesday, October 21st, 2014

wegmansI was quite thrilled when I heard that our customer Wegmans got ranked by Consumer Reports as the #1 supermarket chain in the US.

Wegmans have been long-time customers of NServiceBus and I recently got the opportunity to go on a guided tour in their flagship store in Rochester and hear all the ways that they’ve been leveraging our platform – even the scales that people use to weigh their produce are linked up.

Yup – you may even be eating NServiceBus and not know it 🙂

There are also some pretty powerful back-office processes at play – things that your regular consumer wouldn’t even notice but that matter quite a bit.

In any case, I’ll hand this over to Adam Fyles – the person who has done the actual work of getting NServiceBus into Wegmans, from the early proof-of-concept days to leveraging it across the enterprise to tell the story himself.

Here’s Adam presenting at NSBCon USA 2014:

And if you want the slides or to hear more from Adam, check out his blog at: http://adamfyles.blogspot.com/.

For more information on NServiceBus and the rest of the Particular Service Platform, check out http://particular.net/

NSBCon London 2014 Wrap-up

Tuesday, August 5th, 2014

Well, NSBCon London was a blast. It was such a blast that it took me this long to recover and get my head back into blogging. In any case, for those of you who couldn’t make it, check out this short 2-min video to get a feel for what it was like:

The venue was packed, the speakers were great, and all in all the conference was a smashing success. If you don’t believe me <wink/> you can check out Roy Cornelissen’s coverage here.

All videos now online

For those of you who couldn’t make it, we have all the videos recorded for you and you can access them here.

Some of the cooler demos included:

  • Szymon Pobiega showing how he plugged the Event Store under NServiceBus for complete transport, subscription, timeout, and saga persistence – video here
  • Dylan Beattie videoing the audience with his iPhone and having that processed through NServiceBus and uploaded to their site in “real time” – check it out

Of course, I really think you should check out the full list.

Onward – to New York

NSBCon New YorkAnd for those of you in the US and Canada, we’re happy to announce that registration is open for NSBCon New York!

The early bird is available until the end of this week (Aug 8), so you should really get going.

Register here.

We’ve got some really great speakers lined up for you – Jimmy Bogard will be there, and we’ll have both Oren Eini and Ted Neward speaking as well (who you might remember from the infamous ORM Smackdown).

And Carl and Richard from Dot Net Rocks will be there as well – rockin’ it the way that only DNR can.

Hope to see you there!

Service-Oriented Composition (with video)

Wednesday, July 30th, 2014

When telling people about my approach to SOA, in which a given service would have client/browser-side components running side-by-side in the same process and even in the same page as components from other services, I often get asked this question:

“Doesn’t all of this loosely-coupled composition come with a high cost, in terms of client to server chit-chat?”

So, I’ve finally buckled down and put together a slide to illustrate how the technocratic IT/Ops service I’ve talked about in the past can provide components to resolve these sorts of problems.

After putting the slide together, and realizing some animation would do it good, I went and made a short (5 min) video including some verbal explanation as to how it all works – just for clarity. Check it out or watch it here:

And here’s the image showing everything in one picture:

Service-oriented composition


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Bryan Wheeler, Director Platform Development at msnbc.com
Udi Dahan is the real deal.

We brought him on site to give our development staff the 5-day “Advanced Distributed System Design” training. The course profoundly changed our understanding and approach to SOA and distributed systems.

Consider some of the evidence: 1. Months later, developers still make allusions to concepts learned in the course nearly every day 2. One of our developers went home and made her husband (a developer at another company) sign up for the course at a subsequent date/venue 3. Based on what we learned, we’ve made constant improvements to our architecture that have helped us to adapt to our ever changing business domain at scale and speed If you have the opportunity to receive the training, you will make a substantial paradigm shift.

If I were to do the whole thing over again, I’d start the week by playing the clip from the Matrix where Morpheus offers Neo the choice between the red and blue pills. Once you make the intellectual leap, you’ll never look at distributed systems the same way.

Beyond the training, we were able to spend some time with Udi discussing issues unique to our business domain. Because Udi is a rare combination of a big picture thinker and a low level doer, he can quickly hone in on various issues and quickly make good (if not startling) recommendations to help solve tough technical issues.” November 11, 2010

Sam Gentile Sam Gentile, Independent WCF & SOA Expert
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A man I respect immensely.”

Ian Robinson Ian Robinson, Principal Consultant at ThoughtWorks
"Your blog and articles have been enormously useful in shaping, testing and refining my own approach to delivering on SOA initiatives over the last few years. Over and against a certain 3-layer-application-architecture-blown-out-to- distributed-proportions school of SOA, your writing, steers a far more valuable course."

Shy Cohen Shy Cohen, Senior Program Manager at Microsoft
“Udi is a world renowned software architect and speaker. I met Udi at a conference that we were both speaking at, and immediately recognized his keen insight and razor-sharp intellect. Our shared passion for SOA and the advancement of its practice launched a discussion that lasted into the small hours of the night.
It was evident through that discussion that Udi is one of the most knowledgeable people in the SOA space. It was also clear why – Udi does not settle for mediocrity, and seeks to fully understand (or define) the logic and principles behind things.
Humble yet uncompromising, Udi is a pleasure to interact with.”

Glenn Block Glenn Block, Senior Program Manager - WCF at Microsoft
“I have known Udi for many years having attended his workshops and having several personal interactions including working with him when we were building our Composite Application Guidance in patterns & practices. What impresses me about Udi is his deep insight into how to address business problems through sound architecture. Backed by many years of building mission critical real world distributed systems it is no wonder that Udi is the best at what he does. When customers have deep issues with their system design, I point them Udi's way.”

Karl Wannenmacher Karl Wannenmacher, Senior Lead Expert at Frequentis AG
“I have been following Udi’s blog and podcasts since 2007. I’m convinced that he is one of the most knowledgeable and experienced people in the field of SOA, EDA and large scale systems.
Udi helped Frequentis to design a major subsystem of a large mission critical system with a nationwide deployment based on NServiceBus. It was impressive to see how he took the initial architecture and turned it upside down leading to a very flexible and scalable yet simple system without knowing the details of the business domain. I highly recommend consulting with Udi when it comes to large scale mission critical systems in any domain.”

Simon Segal Simon Segal, Independent Consultant
“Udi is one of the outstanding software development minds in the world today, his vast insights into Service Oriented Architectures and Smart Clients in particular are indeed a rare commodity. Udi is also an exceptional teacher and can help lead teams to fall into the pit of success. I would recommend Udi to anyone considering some Architecural guidance and support in their next project.”

Ohad Israeli Ohad Israeli, Chief Architect at Hewlett-Packard, Indigo Division
“When you need a man to do the job Udi is your man! No matter if you are facing near deadline deadlock or at the early stages of your development, if you have a problem Udi is the one who will probably be able to solve it, with his large experience at the industry and his widely horizons of thinking , he is always full of just in place great architectural ideas.
I am honored to have Udi as a colleague and a friend (plus having his cell phone on my speed dial).”

Ward Bell Ward Bell, VP Product Development at IdeaBlade
“Everyone will tell you how smart and knowledgable Udi is ... and they are oh-so-right. Let me add that Udi is a smart LISTENER. He's always calibrating what he has to offer with your needs and your experience ... looking for the fit. He has strongly held views ... and the ability to temper them with the nuances of the situation.
I trust Udi to tell me what I need to hear, even if I don't want to hear it, ... in a way that I can hear it. That's a rare skill to go along with his command and intelligence.”

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“We hired Udi as a SOA specialist for a large scale project. The development is outsourced to India. SOA is a buzzword used almost for anything today. We wanted to understand what SOA really is, and what is the meaning and practice to develop a SOA based system.
We identified Udi as the one that can put some sense and order in our minds. We started with a private customized SOA training for the entire team in Israel. After that I had several focused sessions regarding our architecture and design.
I will summarize it simply (as he is the software simplist): We are very happy to have Udi in our project. It has a great benefit. We feel good and assured with the knowledge and practice he brings. He doesn’t talk over our heads. We assimilated nServicebus as the ESB of the project. I highly recommend you to bring Udi into your project.”

Catherine Hole Catherine Hole, Senior Project Manager at the Norwegian Health Network
“My colleagues and I have spent five interesting days with Udi - diving into the many aspects of SOA. Udi has shown impressive abilities of understanding organizational challenges, and has brought the business perspective into our way of looking at services. He has an excellent understanding of the many layers from business at the top to the technical infrstructure at the bottom. He is a great listener, and manages to simplify challenges in a way that is understandable both for developers and CEOs, and all the specialists in between.”

Yoel Arnon Yoel Arnon, MSMQ Expert
“Udi has a unique, in depth understanding of service oriented architecture and how it should be used in the real world, combined with excellent presentation skills. I think Udi should be a premier choice for a consultant or architect of distributed systems.”

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“When we were faced with a task of creating a high performance server for a video-tele conferencing domain we decided to opt for a stateless cluster with SQL server approach. In order to confirm our decision we invited Udi.

After carefully listening for 2 hours he said: "With your kind of high availability and performance requirements you don’t want to go with stateless architecture."

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It was a distinct pleasure and a unique opportunity to learn from someone who is among the best at what he does.”

Jack Van Hoof Jack Van Hoof, Enterprise Integration Architect at Dutch Railways
“Udi is a respected visionary on SOA and EDA, whose opinion I most of the time (if not always) highly agree with. The nice thing about Udi is that he is able to explain architectural concepts in terms of practical code-level examples.”

Neil Robbins Neil Robbins, Applications Architect at Brit Insurance
“Having followed Udi's blog and other writings for a number of years I attended Udi's two day course on 'Loosely Coupled Messaging with NServiceBus' at SkillsMatter, London.

I would strongly recommend this course to anyone with an interest in how to develop IT systems which provide immediate and future fitness for purpose. An influential and innovative thought leader and practitioner in his field, Udi demonstrates and shares a phenomenally in depth knowledge that proves his position as one of the premier experts in his field globally.

The course has enhanced my knowledge and skills in ways that I am able to immediately apply to provide benefits to my employer. Additionally though I will be able to build upon what I learned in my 2 days with Udi and have no doubt that it will only enhance my future career.

I cannot recommend Udi, and his courses, highly enough.”

Nick Malik Nick Malik, Enterprise Architect at Microsoft Corporation
You are an excellent speaker and trainer, Udi, and I've had the fortunate experience of having attended one of your presentations. I believe that you are a knowledgable and intelligent man.”

Sean Farmar Sean Farmar, Chief Technical Architect at Candidate Manager Ltd
“Udi has provided us with guidance in system architecture and supports our implementation of NServiceBus in our core business application.

He accompanied us in all stages of our development cycle and helped us put vision into real life distributed scalable software. He brought fresh thinking, great in depth of understanding software, and ongoing support that proved as valuable and cost effective.

Udi has the unique ability to analyze the business problem and come up with a simple and elegant solution for the code and the business alike.
With Udi's attention to details, and knowledge we avoided pit falls that would cost us dearly.”

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“Udi delivered a 5 hour long workshop on SOA for aspiring architects in Norway. While keeping everyone awake and excited Udi gave us some great insights and really delivered on making complex software challenges simple. Truly the software simplist.”

Motty Cohen, SW Manager at KorenTec Technologies
“I know Udi very well from our mutual work at KorenTec. During the analysis and design of a complex, distributed C4I system - where the basic concepts of NServiceBus start to emerge - I gained a lot of "Udi's hours" so I can surely say that he is a professional, skilled architect with fresh ideas and unique perspective for solving complex architecture challenges. His ideas, concepts and parts of the artifacts are the basis of several state-of-the-art C4I systems that I was involved in their architecture design.”

Aaron Jensen Aaron Jensen, VP of Engineering at Eleutian Technology
Awesome. Just awesome.

We’d been meaning to delve into messaging at Eleutian after multiple discussions with and blog posts from Greg Young and Udi Dahan in the past. We weren’t entirely sure where to start, how to start, what tools to use, how to use them, etc. Being able to sit in a room with Udi for an entire week while he described exactly how, why and what he does to tackle a massive enterprise system was invaluable to say the least.

We now have a much better direction and, more importantly, have the confidence we need to start introducing these powerful concepts into production at Eleutian.”

Gad Rosenthal Gad Rosenthal, Department Manager at Retalix
“A thinking person. Brought fresh and valuable ideas that helped us in architecting our product. When recommending a solution he supports it with evidence and detail so you can successfully act based on it. Udi's support "comes on all levels" - As the solution architect through to the detailed class design. Trustworthy!”

Chris Bilson Chris Bilson, Developer at Russell Investment Group
“I had the pleasure of attending a workshop Udi led at the Seattle ALT.NET conference in February 2009. I have been reading Udi's articles and listening to his podcasts for a long time and have always looked to him as a source of advice on software architecture.
When I actually met him and talked to him I was even more impressed. Not only is Udi an extremely likable person, he's got that rare gift of being able to explain complex concepts and ideas in a way that is easy to understand.
All the attendees of the workshop greatly appreciate the time he spent with us and the amazing insights into service oriented architecture he shared with us.”

Alexey Shestialtynov Alexey Shestialtynov, Senior .Net Developer at Candidate Manager
“I met Udi at Candidate Manager where he was brought in part-time as a consultant to help the company make its flagship product more scalable. For me, even after 30 years in software development, working with Udi was a great learning experience. I simply love his fresh ideas and architecture insights.
As we all know it is not enough to be armed with best tools and technologies to be successful in software - there is still human factor involved. When, as it happens, the project got in trouble, management asked Udi to step into a leadership role and bring it back on track. This he did in the span of a month. I can only wish that things had been done this way from the very beginning.
I look forward to working with Udi again in the future.”

Christopher Bennage Christopher Bennage, President at Blue Spire Consulting, Inc.
“My company was hired to be the primary development team for a large scale and highly distributed application. Since these are not necessarily everyday requirements, we wanted to bring in some additional expertise. We chose Udi because of his blogging, podcasting, and speaking. We asked him to to review our architectural strategy as well as the overall viability of project.
I was very impressed, as Udi demonstrated a broad understanding of the sorts of problems we would face. His advice was honest and unbiased and very pragmatic. Whenever I questioned him on particular points, he was able to backup his opinion with real life examples. I was also impressed with his clarity and precision. He was very careful to untangle the meaning of words that might be overloaded or otherwise confusing. While Udi's hourly rate may not be the cheapest, the ROI is undoubtedly a deal. I would highly recommend consulting with Udi.”

Robert Lewkovich, Product / Development Manager at Eggs Overnight
“Udi's advice and consulting were a huge time saver for the project I'm responsible for. The $ spent were well worth it and provided me with a more complete understanding of nServiceBus and most importantly in helping make the correct architectural decisions earlier thereby reducing later, and more expensive, rework.”

Ray Houston Ray Houston, Director of Development at TOPAZ Technologies
“Udi's SOA class made me smart - it was awesome.

The class was very well put together. The materials were clear and concise and Udi did a fantastic job presenting it. It was a good mixture of lecture, coding, and question and answer. I fully expected that I would be taking notes like crazy, but it was so well laid out that the only thing I wrote down the entire course was what I wanted for lunch. Udi provided us with all the lecture materials and everyone has access to all of the samples which are in the nServiceBus trunk.

Now I know why Udi is the "Software Simplist." I was amazed to find that all the code and solutions were indeed very simple. The patterns that Udi presented keep things simple by isolating complexity so that it doesn't creep into your day to day code. The domain code looks the same if it's running in a single process or if it's running in 100 processes.”

Ian Cooper Ian Cooper, Team Lead at Beazley
“Udi is one of the leaders in the .Net development community, one of the truly smart guys who do not just get best architectural practice well enough to educate others but drives innovation. Udi consistently challenges my thinking in ways that make me better at what I do.”

Liron Levy, Team Leader at Rafael
“I've met Udi when I worked as a team leader in Rafael. One of the most senior managers there knew Udi because he was doing superb architecture job in another Rafael project and he recommended bringing him on board to help the project I was leading.
Udi brought with him fresh solutions and invaluable deep architecture insights. He is an authority on SOA (service oriented architecture) and this was a tremendous help in our project.
On the personal level - Udi is a great communicator and can persuade even the most difficult audiences (I was part of such an audience myself..) by bringing sound explanations that draw on his extensive knowledge in the software business. Working with Udi was a great learning experience for me, and I'll be happy to work with him again in the future.”

Adam Dymitruk Adam Dymitruk, Director of IT at Apara Systems
“I met Udi for the first time at DevTeach in Montreal back in early 2007. While Udi is usually involved in SOA subjects, his knowledge spans all of a software development company's concerns. I would not hesitate to recommend Udi for any company that needs excellent leadership, mentoring, problem solving, application of patterns, implementation of methodologies and straight out solution development.
There are very few people in the world that are as dedicated to their craft as Udi is to his. At ALT.NET Seattle, Udi explained many core ideas about SOA. The team that I brought with me found his workshop and other talks the highlight of the event and provided the most value to us and our organization. I am thrilled to have the opportunity to recommend him.”

Eytan Michaeli Eytan Michaeli, CTO Korentec
“Udi was responsible for a major project in the company, and as a chief architect designed a complex multi server C4I system with many innovations and excellent performance.”

Carl Kenne Carl Kenne, .Net Consultant at Dotway AB
“Udi's session "DDD in Enterprise apps" was truly an eye opener. Udi has a great ability to explain complex enterprise designs in a very comprehensive and inspiring way. I've seen several sessions on both DDD and SOA in the past, but Udi puts it in a completly new perspective and makes us understand what it's all really about. If you ever have a chance to see any of Udi's sessions in the future, take it!”

Avi Nehama, R&D Project Manager at Retalix
“Not only that Udi is a briliant software architecture consultant, he also has remarkable abilities to present complex ideas in a simple and concise manner, and...
always with a smile. Udi is indeed a top-league professional!”

Ben Scheirman Ben Scheirman, Lead Developer at CenterPoint Energy
“Udi is one of those rare people who not only deeply understands SOA and domain driven design, but also eloquently conveys that in an easy to grasp way. He is patient, polite, and easy to talk to. I'm extremely glad I came to his workshop on SOA.”

Scott C. Reynolds Scott C. Reynolds, Director of Software Engineering at CBLPath
“Udi is consistently advancing the state of thought in software architecture, service orientation, and domain modeling.
His mastery of the technologies and techniques is second to none, but he pairs that with a singular ability to listen and communicate effectively with all parties, technical and non, to help people arrive at context-appropriate solutions. Every time I have worked with Udi, or attended a talk of his, or just had a conversation with him I have come away from it enriched with new understanding about the ideas discussed.”

Evgeny-Hen Osipow, Head of R&D at PCLine
“Udi has helped PCLine on projects by implementing architectural blueprints demonstrating the value of simple design and code.”

Rhys Campbell Rhys Campbell, Owner at Artemis West
“For many years I have been following the works of Udi. His explanation of often complex design and architectural concepts are so cleanly broken down that even the most junior of architects can begin to understand these concepts. These concepts however tend to typify the "real world" problems we face daily so even the most experienced software expert will find himself in an "Aha!" moment when following Udi teachings.
It was a pleasure to finally meet Udi in Seattle Alt.Net OpenSpaces 2008, where I was pleasantly surprised at how down-to-earth and approachable he was. His depth and breadth of software knowledge also became apparent when discussion with his peers quickly dove deep in to the problems we current face. If given the opportunity to work with or recommend Udi I would quickly take that chance. When I think .Net Architecture, I think Udi.”

Sverre Hundeide Sverre Hundeide, Senior Consultant at Objectware
“Udi had been hired to present the third LEAP master class in Oslo. He is an well known international expert on enterprise software architecture and design, and is the author of the open source messaging framework nServiceBus. The entire class was based on discussion and interaction with the audience, and the only Power Point slide used was the one showing the agenda.
He started out with sketching a naive traditional n-tier application (big ball of mud), and based on suggestions from the audience we explored different solutions which might improve the solution. Whatever suggestions we threw at him, he always had a thoroughly considered answer describing pros and cons with the suggested solution. He obviously has a lot of experience with real world enterprise SOA applications.”

Raphaël Wouters Raphaël Wouters, Owner/Managing Partner at Medinternals
“I attended Udi's excellent course 'Advanced Distributed System Design with SOA and DDD' at Skillsmatter. Few people can truly claim such a high skill and expertise level, present it using a pragmatic, concrete no-nonsense approach and still stay reachable.”

Nimrod Peleg Nimrod Peleg, Lab Engineer at Technion IIT
“One of the best programmers and software engineer I've ever met, creative, knows how to design and implemet, very collaborative and finally - the applications he designed implemeted work for many years without any problems!

Jose Manuel Beas
“When I attended Udi's SOA Workshop, then it suddenly changed my view of what Service Oriented Architectures were all about. Udi explained complex concepts very clearly and created a very productive discussion environment where all the attendees could learn a lot. I strongly recommend hiring Udi.”

Daniel Jin Daniel Jin, Senior Lead Developer at PJM Interconnection
“Udi is one of the top SOA guru in the .NET space. He is always eager to help others by sharing his knowledge and experiences. His blog articles often offer deep insights and is a invaluable resource. I highly recommend him.”

Pasi Taive Pasi Taive, Chief Architect at Tieto
“I attended both of Udi's "UI Composition Key to SOA Success" and "DDD in Enterprise Apps" sessions and they were exceptionally good. I will definitely participate in his sessions again. Udi is a great presenter and has the ability to explain complex issues in a manner that everyone understands.”

Eran Sagi, Software Architect at HP
“So far, I heard about Service Oriented architecture all over. Everyone mentions it – the big buzz word. But, when I actually asked someone for what does it really mean, no one managed to give me a complete satisfied answer. Finally in his excellent course “Advanced Distributed Systems”, I got the answers I was looking for. Udi went over the different motivations (principles) of Services Oriented, explained them well one by one, and showed how each one could be technically addressed using NService bus. In his course, Udi also explain the way of thinking when coming to design a Service Oriented system. What are the questions you need to ask yourself in order to shape your system, place the logic in the right places for best Service Oriented system.

I would recommend this course for any architect or developer who deals with distributed system, but not only. In my work we do not have a real distributed system, but one PC which host both the UI application and the different services inside, all communicating via WCF. I found that many of the architecture principles and motivations of SOA apply for our system as well. Enough that you have SW partitioned into components and most of the principles becomes relevant to you as well. Bottom line – an excellent course recommended to any SW Architect, or any developer dealing with distributed system.”

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