{"slug":"cold-sms-engine-architecture","title":"N8N Cold SMS Engine: Slot-Based Sending with Quota Management","tags":["n8n","sms","cold-outreach","signal-house","automation"],"agent_summary":"Architecture of an N8N-based cold SMS engine that fires daily, manages lead inventory by slot, handles quota limits, logging, CTA failures, and loops for remaining capacity — all backed by Supabase.","trigger_phrases":["cold sms engine n8n","sms sending workflow architecture","slot based sms sending","n8n sms automation with quota","signal house n8n integration","bulk sms sending system"],"runnable":false,"markdown":"## N8N Cold SMS Engine Architecture\n\n### Overview\nFour interconnected N8N workflows that manage cold SMS outreach at scale through Signal House, backed by Supabase.\n\n### Flow\n1. **Fires at 9:00 AM** — Daily scheduled trigger\n2. **Get leads** — Pulls leads that need to be sent messages today\n3. **Determine slot** — Checks if proper lead count is available for the sending slot\n4. **Check inventory** — Routes leads by slot allocation\n5. **Pick leads** — Select specific leads for this batch\n6. **Send message** — Execute SMS send via Signal House\n7. **Log it** — Record send status, timestamp, message content in Supabase\n8. **CTA failure handling** — Handle failed sends with callback logic\n9. **Quota check** — If more room in quota AND more leads available → loop back and send more\n10. **Complete** — End when quota exhausted or all leads sent\n\n### Key Design Points\n- All connected to Supabase backend for state management\n- Supports pause/resume (can pause SMS sending at will without breaking the system)\n- Handles ~1,000 new leads/day\n- Uses Signal House for sending (cheaper for high volume outbound: ~7 cents/SMS)\n- Reply classification handled by separate N8N workflow that routes to Mattermost (Slack alternative)\n\n### Pause Capability\n- Need ability to pause SMS sending when sales team is unavailable\n- Pausing should not break any workflows or lose leads in queue\n- Leads should be held and sent in next available window\n\n### Why Not GHL Native for Agency Outbound\n- GHL has messaging limits on native numbers\n- Limits get hit daily for high-volume cold outreach\n- Signal House bypasses these limits\n- GHL native is fine for client sub-accounts (local service businesses with lower volume)\n","html":"

N8N Cold SMS Engine Architecture

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Overview

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Four interconnected N8N workflows that manage cold SMS outreach at scale through Signal House, backed by Supabase.

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Flow

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    \n
  1. Fires at 9:00 AM — Daily scheduled trigger
    2. \n
  2. Get leads — Pulls leads that need to be sent messages today
    3. \n
  3. Determine slot — Checks if proper lead count is available for the sending slot
    4. \n
  4. Check inventory — Routes leads by slot allocation
    5. \n
  5. Pick leads — Select specific leads for this batch
    6. \n
  6. Send message — Execute SMS send via Signal House
    7. \n
  7. Log it — Record send status, timestamp, message content in Supabase
    8. \n
  8. CTA failure handling — Handle failed sends with callback logic
    9. \n
  9. Quota check — If more room in quota AND more leads available → loop back and send more
    10. \n
  10. Complete — End when quota exhausted or all leads sent
    11. \n
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Key Design Points

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Pause Capability

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Why Not GHL Native for Agency Outbound

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