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Learn NoSQL Fast: MongoDB, Redis and the 4 Database Types in 36 Flashcards

Learn NoSQL with 36 flashcards: key-value, document, wide-column and graph stores, MongoDB, Redis, BSON, CAP theorem and eventual consistency, sorted by family.

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NoSQL is easy to wave at and hard to explain under pressure in an interview. The NoSQL: MongoDB & Redis Basics deck (code GF5914, 36 cards) is compact: four database families, two flagship products, and the consistency trade-offs that decide when you should reach for them. Here's how to make it stick.

Study this deck: NoSQL: MongoDB & Redis Basics

1 / 10
Question

NoSQL originally

Knew itLearning

Tap the card for the answer · swipe right if you knew it, left if not

Sample cards from the deck

FrontBack
Four main types of NoSQL databasesKey-value stores, document stores, wide-column stores, and graph databases
BSONBinary JSON, used by MongoDB for efficient storage and traversal
Where is Redis data typically stored?In memory (RAM), with optional persistence to disk
What data structures does Redis support?Strings, lists, sets, sorted sets, hashes, bitmaps, hyperloglogs, and streams
Does MongoDB support joins?Yes, though not from sharded collections until version 5.1
Eventual consistencyUpdates reach all nodes eventually, which can cause brief stale reads
A document vs a recordRecords share the same fields; documents in a collection may differ completely
Polyglot persistenceUsing several database types together, each for the job it does best

What the 36 cards cover

Key-value stores, document stores, wide-column stores (Cassandra, HBase), graph databases (Neo4j, RedisGraph), Redis, Memcached, MongoDB, DynamoDB, CouchDB, ArangoDB, BSON, collections, schema flexibility, embedding vs denormalization, horizontal vs vertical scaling, the CAP theorem, eventual consistency, stale reads, write-ahead logging, throughput, the YCSB benchmark, and the Bigtable/Dynamo roots of the NoSQL movement.

Study it as a 4-column grid, not 36 loose facts

The deck mixes definitions and products in no particular order. Sort them first:

  • Key-value: cards 3, 4, 16, 17, 32, 34 (Redis, Memcached, DynamoDB)
  • Document: cards 5-8, 14, 15, 20, 22, 28, 31 (MongoDB, BSON, collections)
  • Wide-column: cards 18, 33 (Cassandra)
  • Graph: cards 19, 36

Then drill the cross-cutting cards (CAP, eventual consistency, denormalization, polyglot persistence) last. When a product card comes up, say its family out loud before flipping. That one habit answers the classic "which database would you pick for X?" question.

Three cards to annotate

  • Card 1 ("NoSQL originally"): the term first meant non-SQL / non-relational. "Not only SQL" is the softer reading that came later, so learn both, in that order.
  • Card 10 (CAP theorem): "pick two of three" is the textbook shortcut. The precise version: partitions will happen, so during one you choose between consistency and availability. Add that to the hint; interviewers love the nuance.
  • Card 36 (RedisGraph): Redis ended RedisGraph (end of life January 2025); the open-source fork lives on as FalkorDB. Also worth a margin note on card 4: Redis changed its license in 2024, which spawned the Valkey fork. Card 14 is fine, but tag it with "multi-document ACID since MongoDB 4.0 (2018)".

Once the NoSQL side is solid, pair it with the relational view in our SQL queries, joins and aggregates guide: cards 21-23 here (embedding, denormalization) only make sense against normalized tables and JOINs.

Search for GF5914 in the library on Flip It to start drilling.

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