Salesforce·Software Engineer·Technical Phone Screen
Jun 2026
Salesforce technical phone screen for a software engineer role, pretty much a pure database theory deep dive. The whole thing centered on transaction isolation levels, which I thought I knew well enough until they started pushing on the locking mechanics.
- Walk me through the four standard transaction isolation levels and which anomalies each one prevents.
- Compare the locking strategies used by Repeatable Read and Serializable, specifically around lock granularity like row locks, gap locks, and predicate locks.
- Explain concretely how Serializable prevents phantom reads where Repeatable Read does not, using the locking differences to justify your answer.
“Started fine, rattled off the four levels in order and matched them to dirty reads, non-repeatable reads, phantoms.” The rest of the author's notes on Software Engineer interview at Salesforce, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.
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