n8n Workflow: Scheduled SMS & Voice Outreach (Supabase, Twilio, Retell)

Automate scheduled SMS and voice outreach from Supabase—every 15 minutes

This n8n workflow automatically claims due outreach tasks from Supabase, applies quiet-hours rules, then sends each candidate an SMS via Twilio or initiates a voice call via Retell—with reliable retry/backoff, result tracking, and an optional Slack run summary.

What this workflow does

• Runs on a schedule (or manually): executes every 15 minutes to load runtime settings such as quiet hours, send caps, and provider credentials.
• Claims a batch from Supabase: uses Supabase views/RPC to fetch due outreach enrollments (or a built-in sample queue if Supabase isn’t configured).
• Applies candidate-local quiet hours: evaluates each enrollment against the outreach sequence and weekend/quiet-hour rules.
• Generates exact send context: produces the SMS text or Retell call context and includes an idempotency key to prevent duplicate sends.
• Sends via the right provider:
  • Twilio SMS when SMS is enabled
  • Retell voice calls when voice is enabled
  • Marks items as transient if the required provider isn’t configured
• Classifies outcomes + updates Supabase: records contact attempts and enrollment state changes, flags carrier-level opt-outs returned by Twilio, and updates next-attempt scheduling using backoff/jitter when needed.
• Optional Slack summary: posts a run report when there’s something notable to communicate.

Use cases

• Run outbound re-engagement campaigns for leads or applicants with strict quiet-hours/weekend compliance.
• Orchestrate multi-step outreach sequences across SMS + voice using Supabase as the source of truth.
• Build resilient contacting logic with retry/backoff and carrier opt-out handling for Twilio.

Technical details

• Integrations: Supabase (due queue + updates), Twilio (SMS + opt-out flags), Retell (voice calls), Slack (optional summary).
• n8n nodes/tooling: if, code, no op, merge, sticky note, http request.