Thoughts

Essays on systems & trade-offs

One idea per piece. The trade-off is the whole point.

Jul 2, 2026

Double-entry is 500 years old and still the right data model

The obvious way to store balances — a column you update — is the one that will eventually betray you. Here's why the accountants had it right.

#ledgers#data-modeling#correctness

Jun 25, 2026

Exactly-once is a lie you tell yourself

You can't deliver a message exactly once across a network. What you can do is process at-least-once and make duplicates harmless — which is the real job.

#distributed-systems#payments#idempotency