RethinkDB

Dear Team, Please advise the stack to be used for building Chat Applications that cater to billions of users and work on Mobile as well as desktop. I don't want to use Firebase since it is not fitting into my use case of not using third Party Service Provider. I am comfortable with Java/PHP as a backend. Can we consider RethinkDB, MySQL, and GunDB for the application?

Also looking for Push methodology and not polling one for sending Realtime updates.

Regards Sukesh

We initially chose RethinkDB because of the schema-less document store features, and better durability resilience/story than MongoDB In the end, it didn't work out quite as we expected: there's plenty of scalability issues, it's near impossible to run analytical workloads and small community makes working with Rethink a challenge. We're in process of migrating all our workloads to PostgreSQL and hopefully, we will be able to decommission our RethinkDB deployment soon.

High-speed update-aware storage used in our region server infrastructure; provides a good middle layer for storage of rapidly modified information. RethinkDB

Main database, using it in multiple datacenters in an active-active configuration. RethinkDB