THE WRITE LAST, READ FIRST RULE

Summary from the TLDR Dev newsletter

TigerBeetle, a financial transactions database, uses a system of record and a system of reference (Postgres) to maintain consistency in the absence of transactions. The "Write Last, Read First" principle guarantees data integrity by writing to the system of record last and reading from it first. Idempotent operations are necessary, as the application uses a durable execution framework (Distributed Async Await) that guarantees eventual completion through checkpointing and resumption.