Databases · free flashcards
Database flashcards: SQL, PostgreSQL, MongoDB and Redis
Most performance problems and many bugs trace back to the database. These decks cover the queries you write every day and the internals that explain why a query is slow, a transaction blocks or a cache goes stale, across relational, document and key-value stores.
- Relational and NoSQLSQL and PostgreSQL alongside MongoDB documents and Redis data structures.
- Why, not just howIndexes, isolation levels, MVCC, replication and eviction, explained in a line or two.
- Queries you can runReal SQL, mongosh and redis-cli snippets with highlighted syntax.
Databases decks
SQL
Learn SQL that holds up in production: joins, grouping, NULL semantics, indexes, transactions, window functions and CTEs.
50 cardsPostgreSQL
PostgreSQL know-how: data types, B-tree and GIN indexes, EXPLAIN, isolation levels, MVCC and VACUUM, JSONB, CTEs, window functions, constraints and roles.
50 cardsMongoDB
MongoDB basics: documents and BSON, CRUD in mongosh, query operators, indexes, the aggregation pipeline, embedding vs referencing, replica sets and sharding.
50 cardsRedis
Redis basics: strings, lists, sets, sorted sets, hashes and streams, TTLs, RDB and AOF persistence, pub/sub, caching patterns, eviction and MULTI/EXEC.
50 cardsHow spaced repetition works
- Step 1See a cardRecall the answer before you flip it. Effortful recall is what builds memory.
- Step 2Grade yourselfAgain, Hard, Good or Easy. Each answer sets when the card comes back.
- Step 3Review just in timeCards return right before you would forget them: minutes, then days, then months.
Frequently asked questions
Should I learn SQL or NoSQL first?
SQL first: it carries over to every relational database and helps you judge when a document or key-value store fits better.
Is the PostgreSQL deck beginner friendly?
It assumes basic SQL. Start with the SQL deck, then move on to PostgreSQL for indexes, transactions and JSONB.
What does the Redis deck cover?
Its data types, expiry, persistence, pub/sub, caching patterns and eviction policies.
Start learning databases today
Free forever. Sync your progress, build a streak, get a daily reminder when your cards are ready, and see your stats grow.