I find it odd that there is this widespread meme—on HN, not in the industry—that microservices are never justified. I think everyone recognizes that it makes sense that domain name resolution is performed by an external service, and very few people are out there integrating a recursive DNS resolver and cache into their monolith. And yet, this long-standing division of responsibility never seems to count as an example.
You're certainly misunderstanding me. Microservices are definitely justifiable in plenty of cases, and _services_ even more often. But they _need to be technically justified_ - that's the point I'm making.
The majority of SOA adoption in small-to-medium tech companies is driven by the wrong type of pain, by technical leaders that can see that if they had their domains already split out into services, their problems would not exist, but don't understand that reaching that point involves _solving their problems first_.
Whenever someone on the projects, I’m attached to tries to create a new service, first I asked them what data it works with, and then I ask them what the alternative to making this a service would be. Usually, by the time we start answering the second question, they realize that, actually, adding the service is just more work.
To me, what’s amazing is that in almost no organization is there a requirement to justify technically the addition of a new service, despite the cost and administrative and cognitive overhead of doing so.
_Services_ are obviously a good idea (nobody is arguing something like PostgreSQL or Redis or DNS or what have you should all run in the same process as the web server).
_Microservices_ attract the criticism. It seems to assume something about the optimal size of services ("micro") that probably isn't optimal for all kinds of service you can think of.
It's funny because the term "microservices" picked up in popularity because previously, most "service-oriented architecture" (the old term) implementations in large companies had services that were worked on by dozens or hundreds of developers, at least in my experience. So going from that to services that were worked on by a single development team of ~10 people was indeed a "microservice" relatively speaking.
Now, thanks to massive changes in how software is built (cloud, containers et al) it's a lot more standard for a normal "service" with no prefix to be built by a small team of developers, no micro- prefix needed.
Yeah, my last company had 10 microservices (the entirety of their codebase) managed by a single team when I started. Some of them had fewer than 5 API endpoints (and weren't doing anything complex to justify that).
The smaller the service, the more likely that the overhead of having a separate service exceeds the benefit of doing so. It isn't at all normal for a service to have its own database unless it provides a substantial piece of functionality, for example, and there are non-trivial costs to splitting databases unnecessarily. If you are not very careful, it is a good way to make certain things a dozen times slower and a dozen times more expensive to develop.
> I find it odd that there is this widespread meme—on HN, not in the industry—that microservices are never justified.
Many HN patrons are actually working where the rubber meets the road.
DNS is a poor comparison. Pretty much everything, related to your application or not, needs DNS. On the other hand, the only thing WNGMAN[0]may or may not do, is help with finding the user’s DOB.
> I find it odd that there is this widespread meme—on HN, not in the industry—that microservices are never justified.
There's a few things in play IMO.
One is lack of definition -- what's a "microservice" anyhow? Netflix popularized the idea of microservices literally being a few hundred lines of code maintained by a single developer, and some people believe that's what a microservice is. Others are more lax and see microservices as being maintained by small (4-10 person) development teams.
Another is that most people have not worked at a place where microservices were done well, because they were implemented by CTOs and "software architects" with no experience at companies with 10 developers. There are a lot of problems that come from doing microservices poorly, particularly around building distributed monoliths and operational overhead. It's definitely preferable to have a poorly-built monolith than poorly-built microservice architectures.
I've been at 4 companies that did microservices (in my definition, which is essentially one service per dev team). Three were a great development experience and dev/deploy velocity was excellent. One was a total clusterfuck.
It doesn't lack a definition, there's lots of people talking about this. In general you'll find something like "a small service that solves one problem within a single bounded context".
> It's definitely preferable to have a poorly-built monolith than poorly-built microservice architectures.
I don't know about "definitely" at all. Having worked with some horrible monoliths, I really don't think I agree. Microservices can be done poorly but at minimum there's a fundamental isolation of components. If you don't have any isolation of components it was never even close to microservices/SoA, at which point, is it really a fair criticism?
> It doesn't lack a definition, there's lots of people talking about this. In general you'll find something like "a small service that solves one problem within a single bounded context".
How small is small? Even within this comment section there are people talking about a single developer being the sole maintainer of multiple microservices. I'm a strong advocate of (micro?)service architecture but I would never recommend doing the "all behavior is 100-line lambda functions" approach.
A horrible monolith vs horrible microservices is subjective, of course, but IMO having everything self-contained to one repository, one collection of app servers, etc. at least gives you some hope of salvation, often by building new functionality in separate services, ironically. Horrible microservices that violate data boundaries, i.e. multiple services sharing a database which is a sadly common mistake, is a much harder problem to solve. (both are bad, of course!)
"Small" is a relative term, and not an ideal one, but what it generally means is "no larger than is needed" - that is, if you have one concrete solution within a bounded context, "small" is the code necessary to implement that solution. It's not a matter of LOC.
> IMO having everything self-contained to one repository
I highly recommend keeping all microservices in a single repository. It's even more important in a microservice world to ensure that you can update dependencies across your organization atomically.
> Horrible microservices that violate data boundaries, i.e. multiple services sharing a database which is a sadly common mistake, is a much harder problem to solve.
But that's not microservices. Maybe this is in and of itself an issue of microservice architecture, the fact that people think they're implementing microservices when they're actually just doing SoA, but microservice architecture would absolutely not include multiple services with a single database, that would not be microservices.
So I think the criticism would be "people find it hard to actually implement microservices" and not "microservice architecture leads to these problems", because microservice architecture is going to steer you away from multiple services using one database.
A little off topic but there are even more sinister patterns than the shared database which some architects are actively advocating for, like
1. The "data service" layer, which (if done improperly) is basically just a worse SQL implemented on top of HTTP but still centralised. Though now you can claim it's a shared service instead of a DB.
2. The "fat cache" database - especially common in strongly event-based systems. Basically every service decides to store whatever it needs from events to have lower latency access for common data. Sounds great but in practice leads to (undocumented) duplicate data, which theoretically should be synchronised but since those service-local mirror DBs are usually introduced without central coordination it's bound to desync at some point.
DNS resolution is genuninely reusable, though. Perhaps that's the test: is this something that could concievably be used by others, as a product in itself, or is it tied very heavily to the business and the rest of the "microservices"?
Remember this is how AWS was born, as a set of "microservices" which could start being sold to external customers, like "storage".
qmail probably counts as "microservices" as well, yes. In that case, for security separation of authority in a multi-user environment. Nowadays we don't really do multi-user environments and separation would be by container.
"I find it odd that there is this widespread meme—on HN, not in the industry—that microservices are never justified"
I think the problem is the word "micro". At my company I see a lot of projects that are run by three devs that and have 13 microservices. They are easy to develop but the maintenance overhead is enormous. And they never get shared between projects so you have 5 services that do basically the same.
I rarely see anyone claiming that microservices are never justified. I think the general attitude toward them is due to the amount of Resume Driven Development that happens in the real world.
Eh, I think a lot more of it is caused by optimism than RDD - people who haven't _tried to do it_ look at the mess they've got, and they can see that if it were divided into domain-based services it would be less of a mess.
And the process seems almost straightforward until you _actually try to do it_, and find out that it's actually fractally difficult - by that point you've committed your organization and your reputation to the task, and "hey, that was a mistake, oops" _after_ you've sunk that kind of organizational resources into such a project is a kind of professional suicide.
