SQLite WAL

SQLite Write-Ahead Logging (WAL) enables concurrent readers and writers by shifting database updates to a separate log file.

WAL mode transforms SQLite from a single-user bottleneck into a high-concurrency engine. By writing changes to a separate -wal file instead of the main database (rollback journal), readers no longer block writers: a writer appends to the log while readers access the original file simultaneously. This architecture delivers faster commit performance by requiring only one disk seek and improves throughput for high-traffic applications like edge servers or local caches. Note that WAL requires persistent shared memory (the -shm file) and works best on local filesystems rather than network drives.

https://www.sqlite.org/wal.html