Chat app with graphql subscriptions or socket io

Can I build a chat app with GraphQL subscriptions? Or should I go with socket io instead?

If socket io, can I use it in GraphQL server ?

That is a very broad question, so unfortunately, I can only give you a very broad answer: Yes, you could use subscriptions to implement something like a chat.
If you were to set up, that might live on the same express instance used by your Apollo Server, but apart from existing in the same environment, it would be independent from the ApolloServer instance.

Okay, thanks. I’ll use subscriptions then