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Payments, architecture, written down.

Ledger design, idempotency, event-driven payments, and AI engineering — from someone who shipped the systems, not surveyed them from a slide.

Two inbound POST /payments requests sharing one idempotency key converge on a single idempotency store and a single ledger write; the stored result fans back out as identical responses.
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19 July 2026·12 min read·Avik Ganguly

Idempotency Keys in Payment APIs: Safe Retries Without Double Charges

How idempotency keys stop payment retries from double-charging — and why the key has to be enforced at the ledger write, not just cached at the API gateway.

Read the full guide
More write-ups on the way.

Working through ledger design, event-driven payments, and PCI tokenization next. If there's a payments or architecture question you want answered from the trenches, email avikganguly010@gmail.com and I'll put it on the list.