The lock component supports local stores : Semaphore and Flock.
For locking over distributed servers, remote stores require Memcached or Redis.

MySQL/MariaDB and PostgreSQL are database server typically used by Symfony applications. These DB engines support locking:

• MySQL GET_LOCK https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
• MariaDB GET_LOCK https://mariadb.com/kb/en/library/get_lock/
• PostgreSQL pg_advisory_lock_shared https://www.postgresql.org/docs/9.1/static/functions-admin.html

This locking mencanism is used for session in PdoSessionHandler