Name the common SQL isolation levels and one anomaly each prevents.
PICTURE THIS: DATABASE INDEX
Simple meaning
Read uncommitted can see dirty data.
WHY — SQL instead of guessing?
Why interviewers care about SQL:
who only read docs from people who shipped.
and tied to Backend work.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1Read uncommitted can see
dirty data.
- 2Read committed avoids dirty
reads but still allows non-repeatable reads.
- 3How it works
Repeatable read avoids non-repeatable reads
- 4in PostgreSQL it also
prevents phantoms via MVCC snapshots, while MySQL InnoDB still needs care for phantoms.
- 5Serializable prevents phantoms by
acting as if transactions ran one after another.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Read uncommitted can see dirty data. Read committed avoids dirty reads but still allows non-repeatable reads.