When George Santayana stated that “Those who cannot remember the past are condemned to repeat it.”, he wasn’t talking about technology. When Brenda Michelson and Ed Featherston said much the same thing recently, they were:
It’s a sad fact of life that today’s silver bullet is likely to be yesterday’s junk which was probably the day before yesterday’s silver bullet.
Poor design choices are made for a variety of reasons. Sometimes it’s a matter of ego. Sometimes inadequate analysis is the culprit. Focusing on technology rather than problem-solving can be another pitfall. Even attempts at post-hoc justification of a prior bad decision can drive new mistakes.
An uncritical acceptance of tradition is a significant source of problem designs. Eberhard Wolff recently took a swipe at one old standard:
The stock reason for a tiered/distributed design is scalability. However, it’s not a given that distributing X horizontal layers across Y machines (yielding X/Y instances) will yield better results than Y machines, each with all three layers deployed on the same machine. The context in which this sort of distribution makes sense is far from universal. Even when the costs of distribution are outweighed by the benefits, traditional monolithic horizontal layers will likely be less efficient than vertical slices. One of the purported benefits of microservices is the ability to independently scale according to business concerns (vertical slices organized around bounded contexts) rather technology concerns (horizontal layers).
The mention of microservices brings to mind the problem of jumping on bandwagons. How many applications currently under development are being designed using this architectural style because it’s the “next big thing” rather than because the style fits the problem? Sam Newman, author of O’Reilly’s Building Microservices, in “Microservices for Greenfield?”, even states that he considers the style to be more suitable for evolving an existing system rather than building from scratch:
I remain convinced that it is much easier to partition an existing, “brownfield” system than to do so up front with a new, greenfield system. You have more to work with. You have code you can examine, you can speak to people who use and maintain the system. You also know what ‘good’ looks like – you have a working system to change, making it easier for you to know when you may have got something wrong or been too aggressive in your decision making process.
You also have a system that is actually running. You understand how it operates, how it behaves in production. Decomposition into microservices can cause some nasty performance issues for example, but with a brownfield system you have a chance to establish a healthy baseline before making potentially performance-impacting changes.
I’m certainly not saying ‘never do microservices for greenfield’, but I am saying that the factors above lead me to conclude that you should be cautious. Only split around those boundaries that are very clear at the beginning, and keep the rest on the more monolithic side. This will also give you time to assess how how mature you are from an operational point of view – if you struggle to manage two services, managing 10 is going to be difficult.
This same over-eagerness is present in front-end development as much as back-end development. Stefan Tilkow recently tweeted regarding the trend of jumping straight into complex Javascript framework applications rather than evolving into them based on need:
In my opinion, the key to effective design is being able to give a good answer when asked “why”. Being able to articulate the reasons behind the choices made is critical to justifying them. By reasons, I mean a logical explanations of how the techniques chosen contribute to the desired ends. Neither “X recommends this” nor “This is what everybody’s doing” count. Designing, developing, and evolving software systems is not a game of following a recipe. In the words of Grady Booch:
Form Follows Function 
Very wise words, as always, Gene.
One could say the same about Scrum or Kanban “by the book”, or unit-tests or ant other practice for this matter.
Paraphrasing on the subject, I once met a man who suffered from pain in the knee. He demanded a knee replacement from the doctor. While recovering he realized that physiotherapy for a sprung muscle is a great deal more painful with stitches for a redundant surgery (of course, this is not a true story. No sane doctor would allow muscle physiotherapy before the surgery wounds have healed).
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“One could say the same about Scrum or Kanban “by the book””
Indeed…process is just another system, albeit one running on more complicated “hardware” 🙂
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“One could say the same about Scrum or Kanban “by the book”
I find it ironic how many people take a rigid approach to Agile development.
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