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Comment by onion-soup | Hacker News Reader

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Flexibility and constraint are both useful. (Constraint is one of the reasons to use a finite state machine in the first place.) An overly constrained system can't function, an overly flexible system can't be relied upon. You'll answer your question the day you encounter a problem that NoSQL is a bad fit for, and after you learn SQL it won't feel so alien or complicated. Or maybe that day will never come and you'll never feel the need to learn SQL.

For a motivating example, consider a billing or accounting system. This domain is well known, we probably don't need the ability to rapidly evolve our schema. If we violate the constraints of this system, there may be serious consequences, like spending money we don't have or billing for the service twice.

We could build this system with either an NoSQL or a SQL database, but SQL would seem to me to be the natural choice.

I understand what you're saying, but in the example for accounting, we can also solve this problem using NoSQL. Because the most important feature we're talking about there is transaction support. Similarly, schema-on-write can be provided by a library.

To me it seems like NoSQL works better when there is less to normalize, which is the case with microservices. Those services struggle with the support for a distributed transaction when they have to make a distributed transaction. This problem will be very easily solved in SQL (assuming its not shared to completely denormalize everything for performance).

Note that this normalization problem also shows up in schema-on-write. If multiple people are contributing to a schema from different teams, then it will become hard to maintain a schema-on-write.

NoSQL will bring it's own set of issues right? Too flexible of a system with no built in Validations would mean that they need to be handled somewhere else. If we take the example in the post, refund should not precede awaiting payment, If a new status gets added, it becomes easy to know where the migrations have to be run and in NoSQL, either we write something custom or handle it each time the document is called.

not sure what you are onto but SQL is just old and useless, glad i never had to learn it

Surely that logic should not sit in persistance layer though?

I mean, you shouldn't be throwing shit at the DB and seeing what sticks, but why not have the absolute source of truth also be the validator? CHECK constraints are fairly cheap.

They also derisk deploys of application code. If you deploy a bug that doesn't uphold your constraints, you get failures rather than corruption.

Looks like normal SQL syntax to me. That's not alien to most practitioners.

Alien syntax is not a valid critique

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