Webhook Duplicate Events in Next.js Applications
Webhook providers retry failed deliveries automatically, and your Next.js API routes receive these retries as separate HTTP requests. In development, this usually works fine—events arrive once, handlers process them, and everything appears normal. In production, network timeouts, serverless cold starts, and brief application errors trigger retries that can lead to duplicate processing.
When you’re debugging why a payment webhook fired twice or why users received duplicate notifications, you end up digging through provider dashboards, application logs, and database records trying to piece together the delivery timeline. The handler code itself often looks correct, but the infrastructure around it lacks the visibility and control needed for reliable processing.
This becomes less about fixing handler logic and more about having proper delivery tracking and replay capabilities between the webhook provider and your application.
Why webhook duplicate events happen in production
Webhook providers implement retry logic to handle transient failures, but they can’t distinguish between “handler failed to process” and “handler processed successfully but couldn’t respond in time.” Network issues, serverless cold starts, database connection timeouts, or brief downtime all look like failed deliveries from the provider’s perspective.
Next.js API routes in serverless environments have execution time limits and no persistent state between requests. When a handler takes too long to respond—even if it successfully processes the event—the provider considers it a failure and schedules a retry. The subsequent retry arrives as a completely new request, with no indication that the event was already processed.
Database constraints and idempotency keys help prevent duplicate side effects, but they don’t address the underlying visibility problem. You still need to understand which deliveries succeeded, which ones failed, and why retries occurred in the first place.
Next.js serverless execution and webhook reliability
The serverless execution model adds complexity to webhook handling. API routes don’t maintain memory or state between invocations, making it difficult to implement delivery tracking or custom retry logic within your application. Cold starts can cause initial requests to timeout, triggering immediate retries before your handler has a chance to complete.
Request lifecycle constraints mean your handler needs to process the event and respond within the execution time limit, or the provider will retry. This couples your business logic processing time directly to webhook delivery reliability—a concern that belongs at the infrastructure level, not within your application code.
How HookRelay reduces duplicate event complexity
HookRelay sits between webhook providers and your Next.js application, handling delivery reliability and retry logic separately from your business logic. Instead of providers retrying your API route directly, they deliver to HookRelay, which then handles forwarding, tracking, and replay independently.
When retries occur, HookRelay records each delivery attempt with timestamps and response details. This creates visibility into retry patterns without requiring changes to your handler code. Failed events remain available for inspection and manual replay after you’ve fixed any underlying issues.
The delivery tracking documentation shows how each webhook attempt gets recorded, making it easier to understand when and why duplicates occurred.
What this looks like in a Next.js app
- Point webhook providers at HookRelay endpoints instead of your API routes
- HookRelay forwards events to your application and records each delivery attempt
- Retry logic and failure tracking happen outside your serverless execution environment
- Failed events remain inspectable and replayable without rebuilding infrastructure
- Your handler focuses on business logic while delivery concerns stay at the infrastructure layer
Stripe webhook retries and idempotency
Stripe implements exponential backoff for failed webhook deliveries, with retries occurring over several days. Each retry includes the same idempotency key and event ID, but arrives as a separate HTTP request to your endpoint. Stripe’s dashboard shows delivery attempts, but correlating these with your application’s processing logs requires manual cross-referencing.
Stripe recommends implementing idempotency at the application level, but this doesn’t address the operational complexity of understanding delivery patterns or replaying events after fixing handler issues. The Next.js integration guide covers how webhook forwarding maintains Stripe’s signature verification while providing additional delivery visibility.
When infrastructure-level webhook handling makes sense
This architectural approach becomes useful once webhook processing reliability affects your operations—when you need to understand delivery failures, replay events safely, or debug duplicate processing issues. For early prototypes or applications where occasional missed webhooks are acceptable, the additional infrastructure layer may be unnecessary.
If your webhook handlers are working reliably and you rarely need to debug delivery issues, the complexity of external relay infrastructure might not provide immediate value. The operational benefits become more apparent as webhook volume increases or when processing failures have business impact.
HookRelay handles webhook delivery reliability as an infrastructure concern, letting your Next.js handlers focus on business logic while providing the visibility needed for production debugging. See how delivery attempts are tracked to understand what infrastructure-level webhook reliability looks like in practice.