A verified Discord Interactions (slash-command) endpoint. Checks Discord's Ed25519 request signature with verify_signature before doing any work, answers the PING handshake, logs interactions to Postgres and replies in-channel. Discord signs asymmetrically, so its public key must never be used as an HMAC secret.
An API-layer network firewall — IP allow/deny lists (CIDR + IPv6), proxy-aware client resolution that defeats X-Forwarded-For spoofing, per-IP rate limiting, GeoIP/ASN blocking, monitor mode, and custom deny responses — declared per route. No database required.
The OAuth2 authorization-code flow with refresh, per user - the flow behind every 'connect your Google account' button. Single-use CSRF state, tokens sealed with AES-256-GCM (encrypt_value) and never stored in the clear, transparent refresh driven by an absolute expires_at, and correct handling of providers that send refresh_token only on the FIRST consent.
Receive Shopify order webhooks, verify the base64 X-Shopify-Hmac-Sha256 signature (is_valid_hmac with encoding: base64 — Shopify base64-encodes its digest where GitHub/Stripe/Slack use hex), and upsert orders into Postgres idempotently, with a recent-orders and paid-revenue reporting endpoint.
Approve/Reject buttons in Slack, end to end. Slack posts its interactivity payload as JSON inside a urlencoded `payload` FORM FIELD, so it must be parsed with yaml_to_json before anything can read it, and the signature is over the RAW body. Records the decision, then replaces the original message via response_url so the buttons disappear. Catches chat.postMessage failing as ok:false at HTTP 200, and a double-click is idempotent rather than an error.
Verified Slack slash-command endpoint: checks the X-Slack-Signature HMAC before logging the command to Postgres and replying with an ephemeral message.