Instagram

Signature move

Sharded data, and IDs that never collide

Instagram's scaling turns on one hard problem: splitting its data across many databases so writes stop stacking on a single machine. That only works if every row's id is unique across every shard — so Instagram baked a timestamp, a shard number and a per-shard sequence into each id, unique everywhere and still sortable by time. Photos, meanwhile, never touch the app servers at all: they are served from object storage at the edge, near the user.

Build it yourself

Now try building one of these architectures from a blank canvas — you're scored on the services you place and how you wire them.