Modest architectures. A playful methodology for solid results | by Dmitry Kolomiets

A playful methodology for stable outcomes

Picture by Cristofer Maximilian on Unsplash

It is a brief publish about rules I apply to every part I construct — whether or not it’s a class interface, internet API, Infrastructure as Code (IaC) template, or architectural design.

I didn’t plan for this; I used to be excited about rules for constructing good IaC templates, however I shortly realized that these are the final rules I always use. I put collectively a listing, took the primary letters, and used WordFinder to get a phrase. I used to be amused by how good the phrase was, so I made a decision to put in writing about it. The phrase is:

Modest — not wanting to speak about your skills or achievements and to say that you’re good at one thing, even when you find yourself — used to point out approval.

Longman Dictionary of Contemporary English

The rules are:

  • Significant defaults
  • Orthogonality
  • Documentation
  • Extensibility
  • Safety
  • Testability

So right here we’re, yet another mnemonic acronym. There may be all the time a spot for a brand new one.

Let’s begin with protecting the rules. Simply on your amusement, I’ll present examples from the IaC area as an instance that they’re fairly common.

Significant defaults

Easy issues needs to be easy, complicated issues needs to be attainable.
Alan Kay

Significant defaults assist you to reduce the friction required to make use of your artefact. As with API design, think about the sort methodology in Python:

Notice that by default, type returns the objects in ascending order. You may request descending order by offering a non-default parameter, as proven beneath:

Equally, within the IaC world — think about you’ve got a big CloudFormation stack with tens of parameters. For the sake of the argument, Jaeger Quick Start has more than 50. Nonetheless, all parameters have default values, and also you shouldn’t have to vary them if you wish to strive the Fast Begin out. This frictionless expertise builds up confidence and spurs additional experimentation.


Orthogonality is a crucial precept in software program design. As Wikipedia defines it, an orthogonal operation modifications only one factor with out affecting others. A standard instance is pure functions — pure capabilities shouldn’t have unwanted side effects, and due to this fact, it’s simpler to compose a number of capabilities and purpose about them.

An IaC instance could also be a bit harder to understand. Let’s say now we have a big infrastructure deployment that gives the next choices:

  • DNS: Disabled / Non-public Hosted Zone / Public Hosted Zone
  • Storage backend: In-Reminiscence Storage / Elasticsearch
  • Export metrics: Disabled / Enabled

These are orthogonal choices — you’ll be able to combine and match them as you need, and you’ll all the time get a legitimate mixture:

  • No DNS configuration + In-Reminiscence Storage + Disabled metrics
  • Public DNS + Elasticsearch + Enabled metrics

Approaching IaC design with orthogonality in thoughts often leads to options which might be simpler to check and assist, as all options are unbiased.


Documentation is without doubt one of the most uncared for areas of software program engineering. Good documentation could be very troublesome, and (nearly) no person likes to put in writing it. It isn’t clear what is tougher — creating refined code or writing significant documentation for it.

To be clear, by documentation, I don’t imply feedback like this:

Trivial issues don’t want an evidence. It’s extra about extra concerned snippets that you could’t simply comprehend with out realizing some background data:

Figuring out what you want to doc comes with observe, like every part else. It’s worthwhile to write (and browse!) a variety of documentation to know what beauty like. If unsure, clarify your code to an imaginary pal (or a duck) and take into consideration the issues which will elevate their eyebrows (undecided if geese have the eyebrows, although).

Within the IaC area, documentation performs a central position as properly. What number of instances have you ever seen templates with undocumented parameters so that you needed to guess the proper values you should use? What number of instances have you ever guessed incorrectly?

CloudFormation template with no documentation for parameters

Would it not be higher to have parameters logically grouped, with significant descriptions and hyperlinks to internet pages the place purchasers can get additional data?

A extra polished model with parameters grouped and documented

Bear in mind the final time you complained a couple of sluggish cell software, unintuitive person interface, or crappy error message. That’s how your fellow teammates could really feel working along with your IaC template.

Do higher; they deserve it!


Whether or not you design a category that might be utilized by your teammates or construct a large-scale microservices structure — extensibility is one thing you most likely want to consider. Doubtless, you haven’t envisioned all of the attainable utilization eventualities, so creating an open answer would profit you long run.

Open right here is for O in SOLID — one other in style mnemonic and one thing you could need to keep in mind on your subsequent interview. It could be amusing (for each events) should you discuss MODEST rules along with your interviewer as properly.

An instance from the IaC area: Think about that you simply construct infrastructure for a product and deploy assets that different groups will use— VPC, safety teams, IAM roles, and so on. Later, a unique crew needs to deploy a microservice within the VPC. They might most likely want a VPC ID, a listing of subnets, and possibly a safety group to connect to their service. What could be the method for the crew to retrieve this data?

They will open AWS Console, get the identifiers/ARNs and hardcode them in service configuration information. When you have a number of environments (Dev/Check/Prod) — ask them to repeat the method for every atmosphere (and run).

Certainly we will do higher. What if, as a part of your IaC implementation, we offer a set of SSM parameters with all the required identifiers? Then a service crew can import the bits they want utilizing the well-defined parameter names. Deal with these parameters as your IaC “public interface” — as soon as revealed, it’s a must to preserve them and guarantee backward compatibility.


Safety is a catch-all precept. Should you don’t know the place to start out, begin with safety.

Severely although, you want to take into consideration safety, no matter what you might be constructing. From static code evaluation, container runtime safety instruments, community scanners, log evaluation, anomaly detection, and IaC safety instruments — the spectrum is big. Thoughtworks Technology Radar is an efficient place to start out.


I feel we’ve made superb progress over time — even the legendary Is Unit Testing worth the effort StackOverflow query is closed for feedback.

Let’s postulate the next for the sake of the ultimate MODEST precept: testing is sweet and automatic testing is even higher.

Designing for testability signifies that your artefact might be effectively examined both throughout improvement or by your purchasers throughout integration. Take into consideration load/integration checks the purchasers could need to conduct towards the category/API/IaC/structure you developed.

Persevering with our IaC examples, you are able to do lots to make your IaC code testable. Begin with unit checks on your IaC supplier and think about precise deployment checks for various combos of parameters and goal areas. That is particularly precious if you want to assist non-standard areas, similar to China or GovCloud. Right here is an instance of a TaskCat take a look at file (from quickstart-jaeger repository):

No matter you might be doing, there’s a approach to take a look at it.

Being modest will not be all the time life technique, however designing and constructing MODEST architectures is one thing it’s best to think about.

Apologies for this mischievous nonsense. I might be again with extra critical ideas on distributed tracing and OpenTelemetry shortly.

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