Start here
New to key/value stores? Two short pages: what a key/value store is and the three shapes they come in, then how to read a benchmark number without being fooled by it.
If you have never picked a key/value store before, read these two pages first. The first explains what these databases are and the three shapes they come in, in plain language. The second shows how to read a throughput or latency number so a benchmark cannot fool you.
After that, the scenarios tell you which engine to reach for, with real numbers.
What it is
A key/value store is a database that maps a key to a value. The three internal shapes (B-tree, LSM, hash-log) decide what it is fast and slow at.
Reading the numbers
Throughput, tail latency, durability mode, and space amplification: the four numbers that decide which key/value engine fits, and how each one can mislead you.