Which database should I choose in my case?

Question

MySQL

There will be a large list of values, in the future >1M
It will be necessary to make the following requests from the computer
1) Check if there are certain values ​​already in our list
2) Add certain values ​​​​to the end of the list
There will be many such requests and they will be asynchronous (different requests can be sent simultaneously )

Answer 1

Parallel, not asynchronous.
Take postgres, you can't go wrong.

Answer 2

Those. you do not need the elements themselves, but you just need to check whether you added them or not ?
Take the Bloom filter. It will help you reduce the load on the database.

Answer 3

leveldb