Isolation
ELI5 — The Vibe Check
Isolation means concurrent transactions do not see each other's in-progress changes. If you and your friend both edit the same row at the same time, isolation prevents you from seeing each other's half-done work. It is the 'I' in ACID.
Real Talk
Isolation ensures that concurrent transaction execution results in a state equivalent to serial execution. Different isolation levels (READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, SERIALIZABLE) trade strictness for performance. Higher isolation prevents anomalies like dirty reads, non-repeatable reads, and phantom reads.
When You'll Hear This
"We increased the isolation level to prevent dirty reads." / "Lower isolation improves performance but risks reading stale data."
Related Terms
ACID (Atomicity, Consistency, Isolation, Durability)
ACID is the four guarantees a reliable database makes about transactions. It is the reason you trust a bank's database with your money.
Atomicity
Atomicity means a transaction is all-or-nothing — like an atom that cannot be split.
Consistency
Consistency in databases means a transaction can only bring the database from one valid state to another valid state.
Deadlock
A deadlock is when two things are each waiting for the other to go first, and neither ever does. Thread A holds Lock 1 and wants Lock 2.
Durability
Durability means once the database says 'committed', your data is saved forever — even if the server crashes right after.
Locking
Locking prevents two transactions from modifying the same data at the same time. It is how databases coordinate concurrent access.