Okcupid.com (may find matches without access to the database !?)

Question

I am doing a research project on a popular dating site: OkCupid
I would like to talk about how the database is used.
After reading this explanation from the co-founder of the site, I was very embarrassed.
Statements:

when the user searches for matches on OkCupid, we must do the following:

-Retrieve (from somewhere not in the database) answers to the question, answers to their ideal answers and their question. On average, each user on OkCupid has 250 questions in 3 parts.
- Determine who is suitable for their search, usually a very complex query for several million users. On average, tens of thousands of people qualify, and we need to find out who they are without getting into the database.

How do they do all this without consulting a database?
Here is the link to the message
I appreciate any explanation as to how they do something there.

Answer 1

For this often available information, it can be stored in a database, but also stored in a distributed memory cache (for example, Memcached ).

When a user updates his answer or answers a new question, he updates the cache and database so that the database is never queried.

They could somehow access user responses or specific answers based on the cache key and asynchronously request multiple users and compare the responses.

Just a guess.