Rules for databases

Last updated 29 October 2026

Check your program against these rules before you rely on it: each one keeps commits safe, one writer in charge, or the bill small.

Each rule links to its page, which shows what to write and what not to.

Persist, then act

• Await synced() before anything outside the process acts
• Let gate() hold a handler’s answer
• Record a side effect before you make it
• Bound a wait where someone is waiting

One writer

• Run one instance per database
• When a reset says stop, stop
• Keep the cache directory, and never copy it

Size and cost

• Batch a step’s writes into one transaction
• Write what changed, not the whole state
• Keep each transaction under 128 MiB

SQLite

• Leave the journal mode and the page size alone
• Reach the data only through the connection open() returns

Setup

• Create a database before you open it
• Give each program its own narrowed key
• Create a database where its program runs
• Export a plain SQLite copy, never the cache directory