In this case I think it's proper to consider the database as a service in its own right. This is the way it always used to be done, and there are significant advantages, such as being able to focus on safeguarding the data, and leveraging ACID and constraints/stored procs to make the application code less error-prone.
The downside is you have a potentially hard scalability ceiling, and you have coupling of every downstream service to the schema which means all teams have to coordinate with the DB team for schema changes.
I think startups now always go the vertical services route without thinking too hard about it because A) they all aspire to be Amazon/Facebook/Google even though 99.99% will never face that scale and B) resume-driven development.
To be fair, until companies are willing to pay a premium (1) for working on bad-for-resume projects, this is very rational behavior on the part of the technical team.
1) That is, job listings can't have merely "competitive" or "market rate" salary expectations.
> The downside is you have a potentially hard scalability ceiling
Which 99.9% of projects will never ever hit, and those that do will by that point have become such an extreme scale that significant reengineering should be something that's happening anyway.
This can't be said often enough: Scaling is a luxury problem!
It is far more likely that a company gets a "small", stable user base that provides enough income, than it is to become the next Google.
It doesn't make sense to apply all the complexity for large-scale problems when your user base isn't even small-scale. And if your monolith is structured in a remotely sane way, you can introduce microservices (or whatever will be best practice) later on.
On the other hand, it doesn't hurd to write your code with performance and scalability in mind. Neglecting this too hard may result in bad performance even for the first 10 users. But that's more in the sense of "keep it simple enough so it can be easily restructured later on". And in the sense of "measure performance to know your hot spots" ... and concentrate you efforts there.
> On the other hand, it doesn't hurt to write your code with performance and scalability in mind. Neglecting this too hard may result in bad performance even for the first 10 users.
Absolutely. But the architectural choices you make for making the first 1000 users fast are often the complete opposite of ones you'd have to make to make it "scale" to 100k users.
Service/microservice architectures that I've seen are, from an absolute point of view, hideously inefficient, simply because the component that needs data isn't able to ask for the data from the other component (way across the other side of the architecture) in a precise enough fashion. Cue reams of data being sent to you that you don't need because you need to figure out one small aspect of it. And of course, jsonifying it all and de-jsonifying it a few times for good measure. All this with no transaction safety.
Now, if you're operating at the kind of scale where you know that these specific calls are now part of your business critical requirements, you can spend the effort optimizing the hell out of them and reap the gain of horizontal scalability. Of course, that comes at the expense of flexibility.
The main problem is that micro service based architecture is sold as a silver bullet that takes care of all problems.
Knowledgeable and experienced people know that there is no free lunch, but not every opiniated voice isn't necessarily so, and refuting bullshit takes ten times more effort than producing it, so objections might be handwaved away as backwardness if there is a strong force for a modern architecture.
I mean, more of the same old shit isn't exactly an easy sell either, even if every old bad choice could be rationalized at the time...
As I point out occasionally, Wikipedia is MariaDB front-ended by various caching systems. There's some auxiliary stuff for logging and searching, but its synchronization is not mission critical. Wikipedia is the ninth most popular site on the web. You're probably not going to be bigger than that.
A variation on this would be to put the database behind a service that abstracted over the schema, though that only works for basic CRUD queries and not complex aggregations. This service would probably evolve from the monolith.
It sounds like you're describing ORM-as-API. Which, if you find you need it, great, but I wouldn't try to fool myself that introducing a mediating process like that is all that different from what the language/framework likely already provides (contemporary development frameworks are common). It's just ("just") abstracted to operate on network basis. Actually, what you describe sounds like a reduction in functionality from a non-API model.
Hopefully that parses as English, it's still morning for me.
The downside is you have a potentially hard scalability ceiling, and you have coupling of every downstream service to the schema which means all teams have to coordinate with the DB team for schema changes.
I think startups now always go the vertical services route without thinking too hard about it because A) they all aspire to be Amazon/Facebook/Google even though 99.99% will never face that scale and B) resume-driven development.