Parallel Webhook HTTP Fan-Out with Timing Report in n8n

Send multiple webhook HTTP requests in parallel—and get a timing report to prove it

This n8n workflow performs a true HTTP fan-out: it triggers three internal n8n webhook endpoints concurrently via HTTP POST, simulates independent runtimes, and returns a parallelism timing report (including overlap, ordering, and wall time vs. summed durations) to confirm the tasks ran at the same time.

What this workflow does

• Builds three input items (one per service) containing a target webhook URL and payload.
• Combines items into a single list and sends them as concurrent HTTP POST requests using the HTTP Request node with batching disabled.
• Calls three webhook endpoints—/webhook/service-1, /webhook/service-2, and /webhook/service-3—each starting its own execution.
• Each service handler records startedAt, then waits for a different duration to simulate separate service runtimes, and finally returns JSON with service name, startedAt, endAt, and executionId.
• Aggregates responses and calculates key metrics: overlap, wall time vs summed durations, plus arrival and finish order to verify parallel execution.

Use cases

• Validate whether your n8n design actually runs concurrent webhook calls (not sequentially) before deploying production workflows.
• Benchmark and compare “fan-out” performance for downstream internal services.
• Triage timing issues by analyzing executionId and per-service start/end timestamps.
• Demonstrate parallelism in automation engineering reviews with an evidence-based timing report.

Technical details

• Nodes used: Set, Wait, Merge, Webhook, Sticky Note, HTTP Request.
• Concurrency mechanism: HTTP Request with batching disabled to issue parallel POSTs to internal webhook endpoints.
• Setup: Update https://YOUR-N8N-URL in the service definitions, activate the workflow so the webhook endpoints are available, and optionally adjust wait durations and HTTP Request timeout.