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databases
Query with SQL
Learn SQL by running it. Write real queries against a seeded database and get graded the instant you hit Run — projection, filtering, joins and grouping.
3 chapters · 6 activities · easy Start ▸ systemsScaling systems
Make the call that adds real headroom — for the money. Watch a live architecture take load, spot the binding limit, and pick the strategy the simulator proves is best.
2 chapters · 4 activities · medium Start ▸ foundationsSystems 101
A tiny sampler that checks a few basics — pick an answer and see what happens.
1 chapters · 5 activities · easy Start ▸