In Defence of the Monolith, Part 2

All these architectural discussions seem to assume a kind of black box business system where the microservices vs monolith discussion is an internal one, conducted by and for techies, and limited to a rigid view of the business requirements.

Perhaps the early microservices evangelizers such as Netflix have created this environment - after all, who cares whether Netflix is a monolith or a swarm of microservices as long as billing works and users get content when they want?

There's another strong driver for microservices however, which is customer choice, particularly in SaaS settings.

In our industry (HR software), there is no one right answer, or one business problem - customers demand choice, every customer has slightly different needs, and microservices are indicated because they allow customers to pick and choose. The same is true for most SaaS areas I would say.

As an example, one tiny sub-area of HR software, employee engagement improves when we offer employees meaningful benefits. It turns out that many employees love their pets, and offering pet insurance could be a great perk (the HR space is so big that just this niche within a niche could be a multi-million dollar opportunity for someone with a good offering).

Yet would anyone seriously consider altering a monolithic HR application to add pet insurance management? Never. The only viable solution is a microservice, that does just this, and does it well, and plugs into the rest of the stack via APIs.

tl;dr: in the SaaS world, microservices are sometimes indicated not for architectural reasons, but to support customer choice, which is far more important.

I don't usually find arguing over names to be productive. Your "smaller monolithic" application is my microservice. What's in a name?

But as a customer, if I have a HR app from vendor A, and then I want to add a pet insurance app from vendor B, the last thing I want to do is to roll out some creaky enterprise integration process/framework/product. If those products work together via APIs why should I take any of the burden of integration?

What's in a name? Microservices are fine-grained and operate on a single bounded context, where applications typically have coarser-grained interfaces and involve multiple contexts. I suppose if your pet insurance system were only to provide a constrained list of values of pet insurance products, and provide an interface to associate them with a user ID from the HR monolith, then it's a microservice. (Of course, you've pushed off the integration with the _actual_ pet insurance app somewhere else, but that might be OK.)

"APIs" are an enterprise integration technique [1]. There's nothing inherently creaky or frameworkey about them.

[1] http://www.enterpriseintegrationpatterns.com/patterns/messag...

Monolith has become a buzzword. Is any business software actually not a monolith? I mean does it make business sense to re write everything as a microservice?

As always: it depends. Some organizations would benefit from it because they plan on a trajectory that will cause their software to change repeatedly over a longer period of time. Microservices would make it a lot easier to tackle a portion of the whole and to swap it out with something different, or to remove or add pieces in their entirety.

Monolithic software can be quite good when developed with a good understanding of what you want the future to look like. If the future holds more uncertainty such projects tend to become stale and acquire traits usually associated with legacy projects: hard to impossible to maintain or adapt to new roles, no clear interfaces between sub-sections (if those are identifiable at all) and hard to test.

So no, it's not for everybody and it's not for everywhere, but when applied properly it can make all the difference between maintaining forward momentum and losing it entirely after only a few years in business.

The great power of microservices is they allow a reduction in scope, and that alone is worth quite a bit in the maintenance and understanding departments, in a monolith the whole thing is the scope, and that can kill your ability to reason about a project.