Database Index Lab

Records: 1,000Search Key: 500

Database Index Visualizer – B-Trees & Query Speed

A database index is a data structure that improves the speed of data retrieval at the cost of additional storage and write overhead. Distinct from understanding the overall database system, mastering indexing requires knowing how B-tree and hash indexes are structured internally and how the query planner decides when to use them. This visualizer builds a live B-tree index alongside a sample table so you can run queries and see exactly which nodes are traversed during a lookup versus a full sequential scan.

What you can do in this simulation

Build a B-tree index on a sample table column and watch the tree balance on inserts
Run a SELECT query and see the indexed path highlighted node-by-node
Compare query cost (nodes visited) with and without an index on the same data
Observe how bulk inserts cause page splits and tree rebalancing
Explore how composite indexes differ from single-column indexes on multi-condition queries

Concepts covered

database index · B-tree · query optimization · full table scan · index selectivity · query planner

Related simulations

Browse all Technology simulations →

Free to use in your browser — no signup required. Found a bug or have an idea to make it better? Tell us.

Please wait

Loading technology simulations

The requested content is still loading.

Finished experimenting?

Save one completion to this browser's signed guest ledger, or directly to your account when signed in.