Quick search in the database. What to choose?

Question

Database

Hello dear!
It is necessary to develop a program to work with a constantly growing database. The algorithm of the program is very simple: if the string does not exist in the database, then add it to the database.
The question is that the database is planned to be very large, about a million records and constantly accessing it to check the existence of a particular line. The base does not exist yet, but it is planned that it will be simple in structure, approximately "key-value" ...
I will write in C#.
It would be interesting to know in what format it is best to store the database (XML, JSON, etc. except SQL) and what search algorithm to use so that this business works quickly.

Answer 1

Don't like SQL - use NoSQL like MongoDB . There, at the same time, indexes are supported and all that. You can organize a tree. Or you can use a metric space for custom hashes of strings. It's as you wish.

Answer 2

Look towards the organization of the tree.
Each tree node is a letter in a string.
The best way to store a tree is binary sequences.

Answer 3

A large (really) amount of structured data -> DB
Well, there are already indexes, HP and other performance improvement stories

Answer 4

other than SQL

Well, if not SQL (what are the objective reasons?), then take any key-value base and write to it. Will the search go by the key in whole or in part?
You have now described a standard task for any normal database. Those. the one with the indexes. Reasoning only makes sense if you specify how often rows will be inserted, and what exactly the samples will be.