Databases skill assessment
SQL, modeling, indexing, transactions, and scale.
What it covers
SQL & Queries
Fluent SQL is the baseline expectation in almost every engineering interview and every real job — you'll write joins and aggregations daily, and window functions separate people who can query from people who can analyze.
Data Modeling
The schema you design today is the schema you're stuck migrating for years — normalization prevents data-integrity bugs, but knowing when to denormalize is what keeps queries fast at scale.
Indexing & Performance
An unindexed query that's fine at 1,000 rows can take down production at 10 million — reading query plans and choosing the right index type is how you catch that before users do.
Transactions & Concurrency
Two requests hitting the same row at the same time is where 'it works on my machine' breaks — understanding ACID and isolation levels is what keeps money, inventory, and bookings from silently going wrong.
NoSQL & Scaling
Not every problem fits a relational table — knowing when a document, key-value, or column store beats SQL (and the consistency tradeoffs that come with it) is core to designing systems that scale past one server.
Operations & Reliability
The database is the one piece of infrastructure you truly can't just redeploy — backups, failover, and connection pooling are what turn an outage into a non-event instead of a resume-generating one.
Ready to benchmark your Databases skills?
180 questions · about 5 minutes · see your level and percentile instantly.