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Case Study10 min readFeb 2026

Voice AI in Production: Handling 200+ Calls/Day for a Construction SaaS

Angelina handles real customer calls for Onsite — a construction SaaS. Sub-1s latency, appointment booking, lead qualification. Here's what actually works in production.

Voice AIVapiTwilioProductionConstruction Tech
D

Dhruv Tomar

AI Solutions Architect

Tech Stack

VapiTwilioOpenAI Realtimen8nZoho CRM

Architecture

Incoming call -> Twilio -> Vapi (voice agent) -> n8n webhook -> Zoho CRM update + Google Sheets log + Telegram alert. Fallback to human if confidence < 0.7.
200+ calls/day capacity
Sub-1s voice latency
Rs.47.7L monthly revenue supported
7 department coverage

Everyone demos voice AI with a "book me a restaurant" example. Nobody talks about what happens when a construction site manager calls at 6 AM asking about invoice discrepancies while a bulldozer runs in the background.

  • -Real-World Challenges:
  • -Background noise from construction sites destroys transcription accuracy
  • -Indian English accents with Hindi code-switching need specialized handling
  • -Customers expect immediate CRM updates after calls — not "we'll get back to you"
  • -Downtime during business hours = lost deals

The Stack: Vapi handles the voice agent layer with OpenAI Realtime for sub-1s latency. Twilio manages telephony. Every call triggers an n8n webhook that updates Zoho CRM, logs to Google Sheets, and pings Telegram for the sales team.

The Confidence Threshold: If Angelina's confidence drops below 0.7 on any response, she gracefully transfers to a human rep. No awkward "I don't understand" loops. The handoff includes full conversation context so the rep doesn't ask the customer to repeat anything.

What I Learned: Voice AI in production is 20% AI and 80% infrastructure — retry logic, fallback paths, monitoring, and making sure the CRM update happens even if the webhook fails. The AI part is the easy part.

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