CODEWITHSUNDEEP
databasemicroservices
sebsmgzz
sebsmgzz

Reputation: 571

How to persist data in microservices?

I am getting started in microservices architectures and I have a couple of questions about the data persistence and databases.

So my understanding is each microservice has it's own database (not necessarily, but usually). But given that case, consider a usual social media platform with users, posts and comments. There will be two microservices, a user's microservice and a posts' microservice. The user's database have a users table and the posts' database has posts and comments tables.

My question is on the posts microservice, because each post and comment has an author, so usually we would create the foreign key pointing to the user's table, however this is in a different database. What to do then? From my perspective there are 2 options:

  1. Add the authorId entry to the table but not the foreign key constrain. If so, what would happen in the application whenever we retrieve that user's data from the user's microservice using the authorId and the user's data is gone?
  2. Create an author's table in the posts' database. If so, what data should that table contain other than the user's id?

It just doesn't feel right to duplicate the data that is already in the user's database but it also doesn't feel right to use the user's id without the FK constraint.

Upvotes: 3

Views: 322

Answers (1)

kus
kus

Reputation: 504

One thing to note, data growth is quite different

  • Users -> relatively static data.
  • Posts & Comments -> Dynamic and could be exponentially high compared to users data.

Two microservices design looks good. I would prefer option-1 from your design. Duplication is not bad, In normal database design this is normal to have "Denormalization" for better read performance. This is also helping in decoupling from users table , may help you to choose different database if require. some of your question what if users data is missing and posts is available, this can be handle with business logic and API design.

Upvotes: 0

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