What a journal is
A journal entry groups the postings that belong to one business event. A single payment may touch several accounts, but they share one journal so they commit or fail together and carry common metadata like a timestamp and a reference.
Why group postings
- The group enforces the balanced rule, the postings inside a journal must sum to zero.
- Shared metadata such as the originating transfer id ties the legs together.
- Atomic commit of the whole journal prevents a half recorded event.
Anatomy
A journal has a header with the event details and a list of lines, each line being one posting against one account. The system validates the lines balance before persisting.
Practical notes
- Reject any journal whose lines do not sum to zero before writing.
- Store the journal reference so reversals can point back to the original.
- Keep journals immutable and reverse with a new balanced journal.
Key idea
A journal is one atomic balanced unit of work that bundles all postings for a single business event.