Millions is tiny. Toy even. (I work on what could be called a NoSQL database, unfortunately "NoSQL" is a term without specificity. There's many different ways to be a non-relational database!)
My advise to you is to use Postgresql or, heck, don't over think it, sqlite if it helps you get a MVP done sooner. Do NOT prematurely optimize your architecture. Whatever choice results in you spending less time thinking about this now is the right choice.
In the unlikely event you someday have to deal with billions of messages and scaling problems, a great problem to have, there are people like me who are eager to help in exchange for money.
Lots of people like to throw around the term "big data" just like lots of people incorrectly think that just because google or amazon need XYZ solution that they too need XYZ solution. Lots of people are wrong.
If there exists a motherboard that money can buy, where your entire dataset fits in RAM, it's not "big data".
My advise to you is to use Postgresql or, heck, don't over think it, sqlite if it helps you get a MVP done sooner. Do NOT prematurely optimize your architecture. Whatever choice results in you spending less time thinking about this now is the right choice.
In the unlikely event you someday have to deal with billions of messages and scaling problems, a great problem to have, there are people like me who are eager to help in exchange for money.
Lots of people like to throw around the term "big data" just like lots of people incorrectly think that just because google or amazon need XYZ solution that they too need XYZ solution. Lots of people are wrong.
If there exists a motherboard that money can buy, where your entire dataset fits in RAM, it's not "big data".