6.8 Memory Estimation

One hundred million keys with 16-byte names and 8-byte values hold 2.4 GB of data, yet Redis needs roughly 7 to 9 GB of RAM to store them. The difference is overhead: every key carries bookkeeping that is several times larger than such a small payload. Estimating Redis memory means doing that arithmetic before you choose machines: items times bytes per item, plus overhead, plus headroom.

This lesson sizes one system step by step: a gaming platform with a 10-million-player leaderboard, 10 million user profiles, a Bloom filter over 50 million IDs, and sessions for 1 million active users