Devoxx Poland 2019

It was the second time I was visiting Devoxx. This time in Krakow. The first time it was Antwerp and I liked it a lot.

One of the main worries I had before the conference was related to the changes in the way I approach day-to-day work. I’ve started paying more attention to people rather than technologies. Also, I’ve finally understood that lack of diverse knowledge prevents me from being a more efficient engineer. So I was looking for opportunities to improve the following areas:

  1. Intercommunication skills. This first one is a real problem for introverts like me. Introverts and extroverts are usually separated by whether you lose energy from communication or you gain it. So it was really important for me to find those boundaries between socialization and needs of my personality. I was traveling with the guys I work with daily and respect a lot. However, every trip in a group is sort of a challenge for relationships. You can either spoil these or make stronger. Maintaining the status quo is almost impossible. One of the important aspects here was to get out of the shell and start providing direct feedback to the speakers.
  2. Frontend. I was trying to skip this area for a while. And this decision was far from ideal. I need to learn a lot in the limited time frame at the moment. I also have a need to ramp up on the architectural decisions made for the modern UI frameworks.
  3. Microframeworks. We’re using our own stack at Fitbit and like any real non-hello-world tool it has its own problems. So it was pretty interesting to have a look at possible alternatives and possibly learn from them.
  4. Relax. I expected Krakow to be an amazing place. Having a four-day trip is not only a good chance to see something new around you. Having morning runs when all tourists are still asleep is an amazing way to get acquainted with any city. It’s also an interesting opportunity to get away from daily problems and have a 30,000 feet view on your life as a whole.


Flight to Krakow itself was slightly nervous due to the delays. However, eventually, we got out of the plane on Saturday evening and got a chance to start enjoying Krakow. It’s beautiful and crowdy. We could barely find a place to seat Saturday night. The same happened Sunday afternoon. Too many tourists like us. Still, Krakow is gorgeous. Beautiful river, amazing old buildings and castles, friendly people all over the place.

We also decided to register for the conference in advance not to spend too much time in the queues Monday morning. And it appears to be a pretty good idea. And Devoxx Poland 2019 began for us.



The first thing I’ve noticed was the level of organization in terms of food. All four floors were full of beverages and food. This kind of abundance lasted for the whole conference. Special thanks to organizers for separating out vegetarian buffets for lunch. Queues were way smaller there. Food was pretty good and the coffee was endless.

Lots of interesting booths where you can talk on various topics and get some loot. The amount of marketing and sponsorship support of the conference is impressive. I haven’t seen anything like this during the last times I’ve visited Java conferences in Belarus/Ukraine/Russia.


So let’s begin with talks.

I didn’t find keynotes topics particularly interesting and I’ll be mostly concentrating on the talks I found useful for myself. The first talk I visited was:

Micro Frontends – a Strive for Fully Verticalized Systems

I had no idea what it is all about. I was pretty heads low the last year and it was a good chance for me to get into the topic. And the talk was amazing. It described basic concepts, provided analogies. It can be used as a map of the landscape of the current state of micro-frontends. It was really worth visiting. I didn’t know about isolated CSS. I’m always amazed when the speaker has a good understanding of the solution limitations and does not try to sell a silver bullet for you.

Architect’s Guide to Frontend Frameworks

The same disclaimer about being in a bunker goes here. It looks like frontend stage is getting up to speed and starts incorporating and evolving very interesting architectural patterns introduced by Angular/React/AngularV2/Redux. Things became way more clear for me after the talk.

Stress Driven Development, and How to Avoid It

I really appreciate the fact that our industry is starting to think of people too rather than concentrating on technologies only. And presentation from Dmitry was exactly about how to make you as a human happier. Interestingly I came to similar conclusions myself with slight variations. Was glad to see that I’m far from being alone in this journey. What also makes me happy is that the talk itself evolves, slides change over time along with Dmitry vision.
It was also the first time I’ve heard of the 16/8 fasting model. Doing lots of food experimentation already. Will definitely try it out.



The Survival Guide to Modern Apps AuthN and AuthZ specs

This one served me as a really valuable source of categorized and processed information. I was finally able to match all of these crazy abbreviations in my head. It was even more interesting since we’re considering bringing Keycloack in.

Talk to me nicely – how to communicate your ideas and speed up your career.

It is always good to see when engineers start thinking not only technologies but also about people around them. Lots of us lack good communication skills and soft skills in general. Despite the fact that we’re social animals at the end of the day and that being in a society is one of our base needs. The title of the talk is slightly misleading to my taste. I would say it’s mostly about being a human at the workplace. Ideas formulated in the talk are well-worth revisiting.

Yeah, not too much for the whole day. But maybe I’ve chosen the wrong talks.



7 Deadlier Sins of Craftsmanship

This was an outstanding talk at least due to its format. It’s hard to say how much hours it took to make it that cool. It was the first time I saw Cheerleader effect bias or heard the name of the IKEA effect bias. So this talk is a sort of journey through biases. It’s really good to stop sometimes and ask yourself: “Am I doing this right?”

Resilient service-to-service calls in a post-Hystrix world

This talk was the last one I decided to visit. And it was the best talk out of all I’ve seen during the whole Devoxx PL. You can use slides as a checklist for analyzing your service reliability. This talk also discussed a possible migration path from Hystrix. Bravo, @Rareş. No other talk introduced that much discussion in our team. No other talk has put that much real items in my to-do list. I think talks like these are the best way to show really good engineering culture within the company and to attract smart engineers. Just incredibly happy for one of my former colleagues who has left for N26 last year.


Overall impression

Organization of the event itself was really cool  The quality of the talks varied to a great extent. I really enjoyed some of these, mostly architectural, cultural and practical ones. While lots of talks were not that interesting. From the other side, it was a great pleasure to see that your current employer is in a pretty good shape related to really advanced practices you see at conferences. Sometimes it feels like practices within your team are even more mature and advanced.

Almost all of my goals for the conference were achieved. I’m definitely far from being an early adaptor and still is pretty skeptical about the movements of serverless and micro-frameworks. And things didn’t really change after this conference. At the end of the day, it’s just another tool which might suit your needs or might not.

Still, it was definitely a worth-while time to be spent.


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Certified Scrum Master

Several weeks ago Fitbit gave me a chance to visit CSM training in Bucharest which was held by Ken Rubin. This one was really interesting. It was really fruitful to get some real-world insights from such an experienced coach.

The most important idea I’ve brought home is that Scrum does not bring lots of restrictions. It’s mostly a framework like Spring which provides backbone to your application. But it’s all up to you and your team how to put life around this backbone. This training has also shown a more broad picture of where things come from in my current company. From my point of view it’s not just a framework to develop projects. Things like transparency, lack of position recognition and team responsibilities change the general culture in the company.

This also means that it’s pretty much impossible and probably impractical to bring Scrum into the outsource projects. At least that’s what I see based on the experience for the last 13 years. You can’t have real Scrum unless you have developers who can influence direction of the project. Scrum brings opportunities for the team to choose tasks based on business priority and capacity, not on the last-minute demand of the customer. So it seems like one of the greatest benefit of Scrum is one of the limiting factor for Scrum spreading in Belarusian software development market.

I was slightly disappointed by the exam itself. The questions were rather simple. I would even say that it was not worth doing that much preparation for it. However it might be due to the fact that we are already practicing a good Scrum in our team/company.

Unlike other certifications there is no any supervision for the CSM exam. Exam is not limited in time either. Agile Manifesto and Scrum Guide are more than enough to answer the questions in the exam.

The exam is passed and I can name myself a “Certified Scrum Master” for the next two years. However given the level of certification exam – there are some doubts in having this certificate.

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Machine Learning MOOC

It took a while but finally I’m done. It looks like everyone around me has already passed or abandoned “Machine Learning” MOOC from Stanford University on Coursera. So it was my turn to try this thing out.

Every week I had 2-3 early morning sessions of 2-3 hours each  in order to dive deeper into ML. Theory and quizes took around 2-3 hours each week, another 2-3 hours were spent on practical implementation. My fellow guys reported that parts of the theory were already taught for them in the university  However it was not the case for me. I clearly knew basic parts of working with vectors however things like linear regression were clearly out of scope in my curriculum. Practical tasks were not very difficult however you can always make some stupid mistake and chase it for hours. There were multiple runs of this course already. This means that all of the possible questions, issues and problems were discussed numerous times. Your just need to look for them.

I would say that the course is pretty balanced during weeks 2-9 and requires a bunch of work to be done and efforts to be applied. The last two weeks are pretty easy.

The course itself is amazing. It has a right combination of getting deep enough to get a sense of things, being not very detailed not to sink in maths  and being a good overview of the possible directions in the ML field. There is a lot to learn to become a professional in this field other than this course. However this MOOC definitely serves as an amazing entry point into this area. I really liked the way in which various parts were connected with each other. There was no any part of knowledge given for the sake of it. Every theoretical thing had a really important practical impact. And that’s what I liked the most in the course. It’s very practical and logical. It’s a real fun to see various pieces and ideas glued together to create a real-world output.

Actually it was pretty difficult not to abandon this course for me since it was really intensive. However I’m really happy to have it finished. We already did some application of the knowledge from this course during internal Fitbit hackathon and I guess it’s not the last time it was useful for me.

My huge appreciation to everyone who was involved in creating this course!

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“Working in Teams: A Practical Guide” MOOC

Just finished Working in Teams: A Practical Guide MOOC on edX,

The goal for this course was to get a deeper insights on what can be better in my current team which I joined several months ago. Another intention was to reflect on my previous team and to see what possibilities I had missed.

The course is not really difficult: 7 sections should be passed in one month. Sections are not very big and it won’t take more than an hour per section even with doing all assignments and reviewing your peers. Due to this fact the course does not seem very deep. I would expect more assignments to be done. From the other side external test resources is a great source of understanding on where your team is now.

Key moments I’ve brought from this course:

  1. There is a more or less well-defined theory on team life-cycle and stages effective team passes through
  2. My current team is somewhere in between norming and performing stages according to the Tuckmans’ stages of group development.
  3. Belbin role model for team members seems fun but frankly speaking seems rather abstract. I didn’t find much value of using it in retrospective for some reason.
  4. High level of self-assertiveness is a must-have for a highly effective team along with a high level of communication. I was already coming to this conclusion myself and it was pleasant to see confirmation for it.
  5. There is a set of defined conflict resolution strategies for a team.
  6. Team leadership is a thing which should be done carefully and mindfully. A pretty good theory behind this one is available.

All of these points brought me to an idea that I could do much better in my previous team. I could definitely affect conflict resolution, assertiveness, motivation, communication and leadership aspects of it. This would probably make my previous team a more pleasant place to work.

However it’s all about experience and learning. I’m impressed by the level of communication and assertiveness in my new team. Hopefully techniques discussed in this MOOC will help me in making new team even more effective. This course is definitely well-worth studying so that you can make 8-9 hours you spend each weekday with your team a good and effective investment.

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Oracle Certified Professional: Java SE 8 Programmer

I’m continuing my certification efforts to confirm that I’m a programmer at least to myself.

It took a while to get prepared to the exam but finally I’ve got it passed with 88% of correct answers and got this nice badge.


I can hardly find exam questions difficult or very deep. Still it helped me to get into NIO.2 and ForkJoinPool which I didn’t use a lot during daily job. I can get some sleep now and start preparing my next presentation, probably on ZooKeeper, for the community.

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Elegant Objects. Volume 1

It’s been a while since I’ve first heard of Yegor Bugayenko.

His blog, his conference talks(here, here and here), his podcast participation(here and here) already presented some of the pretty unusual OOP-related ideas. These looked like a bunch of colorful patches to me while they didn’t produce full picture.

So I was looking forward to have a look at the “Elegant Objects. Volume 1” book to see if it can make me a better programmer like it was declared for multiple times all over this book. Many thanks to Kiryl Karatsetski for giving me a chance to read this book.

I’m going split ideas from this book into three sections based on my personal attitude:

  1. Reasonable ideas
  2. Questionable ideas
  3. Harmful ideas

Here’s what I’ve got from this book.

Reasonable ideas

  1. Class naming:
    1. Name class for what it is, not what it does.
    2. “-er” suffix is a sign of something going wrong.
  2. There should be only one primary constructor and probably a bunch of secondary ones which call primary one as a result
  3. No code in constructor.
  4. Choose method names appropriately. It should be either a verb for manipulators or a noun for the builders. Boolean method naming also makes sense.
  5. Fake objects instead of mock objects in tests.
  6. Compact interfaces with the smart helpers inside.
  7. Do not use static methods
  8. Util classes are evil
  9. Method argument can’t be null
  10. Method result can’t be null
  11. Do not use public constants.
  12. Never use getters and setters. At least in your code.
  13. Don’t use type introspection.
  14. Use checked exceptions only

Questionable ideas

  1. Number of constructors can be around 5 to 10.
    Personally I prefer having less constructors and let client adjust things to my input rather than being able to accept whatever a client might pass
  2. Limit number of public methods to 5
    It seems like this concept is an evil when working with the database and you want results based on different queries.
  3. Limit a number of properties to encapsulate to 4.
    My personal number when I start thinking of decomposing the object is around 7.
  4. Always use interfaces.
    This facilitates having too much of a junk code you would never touch. You definitely don’t want to abstract everything you work with.
  5. Use only immutable objects
    It’s an idealistic unusable concept that has nothing in common with the real world programming. Still using immutable objects in the majority of cases is a good thing
  6. Do not use singletons
    It’s really nice that IoC frameworks like Spring can help us to hide complexity of instantiating and using singletons. Still I believe our code will become way more complex to read if we get rid of singletons
  7. Fail fast rather than fail safe
    There are too much conditions here. It might be totally fine if your deployment time is around several minutes and you’re ready to fix production issues any time, day or night. Otherwise you’ll definitely want to appear somewhere in between, probably closer to the “fail safe” side of the fence
  8. Catch exception on the highest level only
    This one is closely related to your position on the “Fail Fast -> Fail Safe” interval.
  9. Use AOP
    Well, it’s a powerful instrument but it’s a real pain for the praised maintainability. It’s a sort magic which appears in runtime from nowhere. Declaration of the pointcuts is really far from the classes which are affected by the aspect and thus not really flexible to work with. Plain Java annotations seem to be a more maintainable choice.
  10. Object should be either final or abstract
    I feel like limiting level of inheritance to just one is a rather good thing. However it’s still difficult to say how it plays with the real code without trying out.

Bad ideas

  1. Optional from JDK8 is a bad thing.
    Well it’s pretty limited in JDK8 and it looks pretty ugly in the code sometimes. Adding Optional::stream in JDK9 is clearly a step in the right direction/
  2. Use multiple level of object nesting to adjust behavior of the nested objects.
    The code becomes complex anf pretty much undebuggable. Those who tried to debug hierarchy of 30+ http filters would probably agree with me.
  3. Don’t use new out of secondary constructors
    Even book example has shown that it does nit make code simpler. Totally looks like an artificial unmaintainable concept.
  4. In the ideal world you would use If class instead of if statement
    I still believe that too much levels of object nesting is evil and makes code unreadable and undebuggable.

The book is definitely worth reading and thinking over the proposed concepts. However it’s really questionable that all of the book recommendations lead to the maintainable code. At least as I see it.

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Presenting “Kafka in Production”

Really glad to tell that my second public presentation really happened at JProf meetup.




This time way less time went into text repetition but way more time went into Kafka-related researches. 🙂
Even though I still have something to tell about Zookeeper – deferring this talk until becoming an OCPJP 8 certified programmer.

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