Use after() for Non-Blocking Operations

Use Next.js's after() to schedule work that should execute after a response is sent. This prevents logging, analytics, and other side effects from blocking the response.

Incorrect (blocks response):

tsx

import {logUserAction} from '@/app/utils'

export async function POST(request: Request) {
  // Perform mutation
  await updateDatabase(request)

  // Logging blocks the response
  const userAgent = request.headers.get('user-agent') || 'unknown'
  await logUserAction({userAgent})

  return new Response(JSON.stringify({status: 'success'}), {
    status: 200,
    headers: {'Content-Type': 'application/json'},
  })
}

Correct (non-blocking):

tsx

import {after} from 'next/server'
import {headers, cookies} from 'next/headers'
import {logUserAction} from '@/app/utils'

export async function POST(request: Request) {
  // Perform mutation
  await updateDatabase(request)

  // Log after response is sent
  after(async () => {
    const userAgent = (await headers()).get('user-agent') || 'unknown'
    const sessionCookie = (await cookies()).get('session-id')?.value || 'anonymous'

    logUserAction({sessionCookie, userAgent})
  })

  return new Response(JSON.stringify({status: 'success'}), {
    status: 200,
    headers: {'Content-Type': 'application/json'},
  })
}

The response is sent immediately while logging happens in the background.

Common use cases:

Analytics tracking
Audit logging
Sending notifications
Cache invalidation
Cleanup tasks

Important notes:

after() runs even if the response fails or redirects
Works in Server Actions, Route Handlers, and Server Components

Reference: https://nextjs.org/docs/app/api-reference/functions/after