Is it ok to use multiple databases within 1 or more microseries?

Question

JavaScript

Good afternoon, please tell me to make the right choice.
Sawing fault-tolerant microservices, is it normal to store user data in one database (for example, in the same postgresql user data) in another database (for example, mongo messages and server settings, as well as a pool of used addresses)?
Whether it is obligatory to use one DB?

Answer 1

The architecture should be built on the principle of saving RAM, if the cost of maintaining several databases is higher than the benefit, then there is no point in breaking it up. It should be understood that different databases have different capabilities.
Therefore, yes, it is normal to use several databases, including storing parameters in files. If it really helps, and does not complicate and waste resources simply because it is.