Idempotency

Documentation from vllnt/convex-idempotency, recorded October 23, 2026. APIs and setup may differ in the Bijection adaptation.

@vllnt/convex-idempotency

Exactly-once idempotency key ledger for retried operations, as a Convex component.

Copy codeconst idem = new Idempotency(components.idempotency);
const claim = await idem.begin(ctx, requestId);   // mints a claim, or short-circuits a replay
if (claim.state === "done") return claim.result;  // replayed — skip the work
// ... run the work ...
await idem.complete(ctx, requestId, result);      // record the outcome for next time

Record an idempotency key with a grace TTL; on a replay short-circuit and return the prior outcome instead of re-running the work. Domain-neutral: payment intents, webhook deliveries, queue consumers, double-submit guards — any operation that must run at most once per key.

Features

• Exactly-once per (scope, key) — begin mints an inflight claim that rides the mutation transaction; a concurrent retry sees inflight with a retryAfterMs backoff hint.
• Replay — once complete records an outcome, a later begin returns { state: "done", result } for a short-circuit.
• Split TTLs — a short inflight lease (default 60s) so a crashed worker's claim self-heals, and a longer done grace (default 24h) after which a key may be re-minted.
• Lost-claim detection — complete returns { recorded: true } | { recorded: false, reason } so a host knows when its work finished but the row was gone. Opt into upsertOnMissing.
• Server-sourced time — expiry is read from the server clock; a caller can't supply now, so an adversarial clock can't force a key to look live or expired.
• TTL validation — non-positive or infinite TTLs throw INVALID_TTL before any write.
• Typed result — Idempotency<TResult> types the stored outcome; a resultValidator narrows it at the boundary.
• Scopes — global by default, or namespace per tenant / operation type.
• Bounded purge + cron — a daily cron sweeps expired keys in batches and self-reschedules until clean.

Installation

Copy codepnpm add @vllnt/convex-idempotency

Peer dependency: convex@^1.41.0.

Usage

Copy code// convex/convex.config.ts
import { defineApp } from "convex/server";
import idempotency from "@vllnt/convex-idempotency/convex.config";

const app = defineApp();
app.use(idempotency);
export default app;

Copy code// convex/charge.ts — host owns auth; pass an opaque idempotency key in.
import { components } from "./_generated/api";
import { mutation } from "./_generated/server";
import { v } from "convex/values";
import { Idempotency } from "@vllnt/convex-idempotency";

const idem = new Idempotency<{ chargeId: string }>(components.idempotency, {
  resultValidator: v.object({ chargeId: v.string() }).parse, // narrow at the boundary
});

export const charge = mutation({
  args: { requestId: v.string(), amount: v.number() },
  handler: async (ctx, { requestId, amount }) => {
    const claim = await idem.begin(ctx, requestId);
    if (claim.state === "done") return claim.result;          // typed replay
    if (claim.state === "inflight")
      throw new Error(`retry in ${claim.retryAfterMs}ms`);    // backoff hint
    const result = { chargeId: await doCharge(amount) };      // state === "fresh"
    const done = await idem.complete(ctx, requestId, result);
    if (!done.recorded) console.warn("claim lost:", done.reason); // work ran, row gone
    return result;
  },
});

API Reference

Full reference: docs/API.md.

React

Backend-only — no ./react entry. Pure infra dedup with no user-facing reactive surface.

Security

• Auth-agnostic — the host resolves identity and decides who may run an operation.
• Tables sandboxed — reached only through the exported functions.
• Server-sourced expiry — a skewed client clock can't hijack a replay or bypass dedup; key / scope / result stay opaque.

See docs/API.md.

Testing

Copy codepnpm test           # single run
pnpm test:coverage  # enforced 100% on covered files

Tests run against the real component runtime via convex-test (@edge-runtime/vm), not mocks.

Contributing

See CONTRIBUTING.md.

Author

Built by bntvllnt · bntvllnt.com · X @bntvllnt

Part of the @vllnt Convex component fleet — vllnt.com

If this is useful, sponsor the work.

License

MIT — see LICENSE.