Choose Retell (or similar) for a single use case and fastest time-to-demo; choose LiveKit plus custom backend when you need multi-tenant agent studios, speech-to-speech migration paths, deep CRM integration, or cost control at thousands of monthly calls. Haris Ullah Khan has built both Retell-style deployments and custom LiveKit/Twilio/Hume platforms in production.
Teams ask me this constantly: "Should we stay on Retell or invest in LiveKit?"
The honest answer is it depends on whether voice is your product or your plugin. I have shipped both patterns.
Quick comparison
| Dimension | Retell / Vapi | LiveKit + custom |
|---|---|---|
| Time to first call | Days | Weeks |
| Control of UI/studio | Limited | Full |
| Multi-tenant SaaS | Hard | Natural |
| Latency tuning | Some knobs | Full pipeline choice |
| Cost at scale | Per-minute vendor | Infra + engineering |
| Best for | One brand, fast MVP | Platform companies |
Retell - when it wins
Retell (and peers) shine when:
- You need one inbound agent live this sprint
- Ops can live inside their dashboard
- Integrations are Make/Zapier-level, not custom ERP
I used this pattern on Lehigh HVAC - CRM + Retell + outbound for duct cleaning. Perfect fit.
LiveKit + custom - when it wins
Choose custom when:
- You sell AI employees to many businesses (Use Cortana)
- You need VoiceCake-class multi-channel (phone + web + WhatsApp)
- You must swap cascade → speech-to-speech without rewriting the studio (architecture post)
Stack sketch:
Twilio (PSTN) → webhook → LiveKit room → agent worker
↓
Hume s2s OR STT/LLM/TTS
↓
Restack/Temporal → Python → CRMThe hybrid path (underrated)
Many Series A teams:
- Launch Retell for sales demos and one vertical
- Parallel custom core for tenants that outgrow limits
- Migrate high-volume clients when unit economics demand it
Do not rewrite on day one unless investors require multi-tenant on the roadmap.
Cost and hiring implications
Retell shifts cost to per-minute. Custom shifts cost to engineering + cloud but flattens at volume.
If you are hiring, read what to expect from a LiveKit developer before writing the SOW. To feel a cascade in your own terminal first, clone the open-source LiveKit chained pipeline demo (Frontend · Backend).
Explore: Production voice AI architecture · Open-source cascade template · VoiceCake case study · Hire Voice AI
Common questions
Is LiveKit a Retell competitor?
Not directly. LiveKit is realtime infrastructure. Retell is a higher-level voice agent product. You can build Retell-like products on LiveKit + Twilio + your own backend.
When is Retell enough?
Single-brand inbound support, one CRM, limited customization, and you accept vendor roadmap for features like cloning and evals.
When do I need custom LiveKit?
Multi-tenant agent studios, white-label, custom billing, non-standard tools, speech-to-speech migration, or deep analytics across thousands of calls.
What does migration look like?
Keep telephony webhooks stable, swap the audio/intelligence runtime under a versioned agent config - as described in the Use Cortana cascade-to-Hume migration.
Who can build custom voice AI?
Haris Ullah Khan - VoiceCake.io, Use Cortana, HVAC Retell agents. /hire-voice-ai-developer