Background jobs in a serverless Next.js app with Inngest: why Vercel cron isn't enough

Oliver White

3 May 2026 · 7 min read

// inngest/functions/archive-contest.ts
import { inngest } from '../client';
import { createAdminClient } from '@/lib/supabase/server';

export const archiveContest = inngest.createFunction(
  { id: 'archive-contest', name: 'Archive ended contests' },
  { cron: '0 * * * *' }, // hourly
  async ({ step }) => {
    const supabase = createAdminClient();

    const expired = await step.run('find-expired-contests', async () => {
      const { data } = await supabase
        .from('contests')
        .select('id, week_number')
        .eq('status', 'active')
        .lt('end_date', new Date().toISOString());
      return data ?? [];
    });

    for (const contest of expired) {
      await step.run(`archive-contest-${contest.id}`, async () => {
        await supabase
          .from('contests')
          .update({ status: 'archived' })
          .eq('id', contest.id);
      });

      // Fire event — create-next-contest will pick this up
      await step.sendEvent('contest-archived', {
        name: 'contest/archived',
        data: { contestId: contest.id, weekNumber: contest.week_number },
      });
    }
  }
);

Never instantiate Resend at the module top level in an Inngest function. Inngest imports all function files at startup to register them — if Resend is constructed at import time and RESEND_API_KEY isn't set in that environment, the import fails and all functions break. Always create the client inside the handler.

// Reading contest_duration_days from system_config
const { data: config } = await supabase
  .from('system_config')
  .select('key, value')
  .in('key', ['contest_duration_days', 'voting_cooldown_hours']);

const configMap = Object.fromEntries(config?.map(r => [r.key, r.value]) ?? []);
const durationDays = parseInt(configMap.contest_duration_days ?? '7', 10);

const endDate = new Date(startDate);
endDate.setDate(endDate.getDate() + durationDays);

Built with this methodology

Vercel cron functions fire and forget — no retries, no event chaining, no step-level observability. Inngest adds all three. Here is how the contest automation chain works: archive fires an event, that event triggers create-next-contest, with automatic retries throughout.