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How a store finds one row among millions, and why the index it builds decides what a query costs.
4 interactive explainers. Each one is a visual story with a live simulation and a knowledge check, and the Ask ViLearn tutor beside all three. Free, and nothing requires an account.
A scan opens every document on every query. Elasticsearch opens them once, while they are written, and builds an index: one row per word, holding the list…
Intermediate · 12 min · Story, simulation and quiz
Without an index the database reads every page of the table to find one row. With one it reads three nodes and a page.
Intermediate · 11 min · Story, simulation and quiz
Ten million banned emails cost about 300 MB to keep in memory. There is a structure that answers the same question in 12 MB and stores no name at all.
Intermediate · 10 min · Story, simulation and quiz
A transaction is one piece of work the database treats as a single unit. It does not stop other people from working.
Intermediate · 9 min · Story, simulation and quiz
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