Figma - the case study

Boards

Every board in the set on one canvas, with a single edit’s path drawn across all of them.

Before you start. You need to have used an app where two people type into the same document at once and neither has to wait for the other. This lesson is the story of what one company had to build so that nobody waits.

The idea in 30 seconds

Figma’s founding move was to stop treating a design document as a file somebody owns, and treat it as a stream of edits ordered by one server.
The thing that can collide is a single property of a single object. When two edits hit the same one, the later arrival wins and the earlier is lost.
Because one server referees every document, nothing needs a timestamp: arrival order is the order.
That referee is one process per open document, affordable only once the 2018 rewrite cut memory to roughly a quarter.
Saving is a journal of every edit plus an occasional full checkpoint, which took the risk window from sixty seconds to 95% of edits safe within 600 milliseconds.
Undo cannot be a rewind when other people are editing. It is a new edit that replays your intention against the document as it now is, and every choice above sends a bill like that one later.

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