Idempotent Lead Webhook Workflow w/ Postgres & HTTP APIs

Prevent duplicate lead processing with an Idempotent Webhook + PostgreSQL

This n8n automation receives lead submissions via a webhook and guarantees that the same Idempotency-Key is processed at most once. If a request is retried, it automatically replays the stored response—so your enrichment, CRM updates, and notifications never run twice for the same lead attempt.

What this workflow does

• Receives a POST webhook containing an Idempotency-Key (and optional X-Client-Id) plus a JSON lead payload.
• Ensures PostgreSQL idempotency support by creating the idempotency_keys table and required indexes (if needed), then validates the request.
• Builds a canonical payload fingerprint to detect mismatched retries.
• Atomically claims or replays:
  • If the Idempotency-Key is new, it claims it with a lease.
  • If the key already exists, it either replays the stored completed response or returns an error for in-progress/mismatched payload/store-unavailable scenarios.
• On first-time processing:
  • Calls an external enrichment API.
  • Computes a deterministic lead score and tier.
  • Creates/updates the lead in a CRM API.
  • Sends a notification via a third HTTP endpoint.
• Stores the final outcome (HTTP status + response body) in PostgreSQL and replies to the webhook with Idempotency-Key and an Idempotent-Replayed flag.

Use cases

• Retry-safe lead intake for SaaS forms, ensuring duplicate webhooks don’t double-enrich or overwrite CRM data.
• Idempotent inbound processing for partner integrations where clients may resend payloads on timeouts.
• Reliable lead routing when enrichment/CRM calls are occasionally slow or transiently unavailable.

Technical details

• PostgreSQL idempotency using idempotency_keys with a lease and stored response replay.
• HTTP APIs for enrichment, CRM updates, and notifications.
• n8n nodes: if, code, wait, webhook, postgres, sticky note.

Setup note: Configure PostgreSQL credentials so the database user can create tables/indexes and read/write the idempotency_keys table.