EXERCISE
1Meet the strictest isolation level that treats your database like there's only one user at a time, ensuring perfect consistency at the cost of performance.
Serializable is like having a strict librarian who only allows one person to read each book at a time - no exceptions!
When your transaction reads a row in Serializable mode, it's not just reading - it's locking. Other transactions can't even read that same row until you're completely done.
-- Transaction 1 (Serializable)
SELECT * FROM users WHERE id = 1; -- Locks the row
-- Transaction 2 tries to read the same row
SELECT * FROM users WHERE id = 1; -- WAITS... and waits...
-- Transaction 1 commits
-- Only now Transaction 2 gets its result!
The Trade-off: Perfect consistency but terrible performance.
It's like having a highway where only one car can drive at a time.
Pro Tip: Serializable eliminates all concurrency issues by essentially eliminating concurrency itself - transactions run as if they're the only one in the database.