You are blatantly wrong and misinformed. You should not make comments like those because people who (just like you) don't know better will take it for truth.

Sqlite does not offer a queing gateway for queries like postgresql or mysql does, but in terms of inherent concurrency it is in fact much more capable than both postgres and mysql is, and with notably higher performance while still consuming less memory. For sheer size of databases, it is faster and more efficient, but only for intra-process concurrency. Contrary to common believe, sqlite does have a transaction log, and it is suitable for multi-process concurrency just not on the same scale as a dbms with a queing gateway.