Member of Technical Staff, Core Backend

Vapi (/ˈVɑːpi/)

• Voice AI that resolves, not transfers
• Powering 1 billion calls for companies like Amazon Ring, Intuit, ServiceTitan, and New York Life
• Trusted by 1 million developers building the future of voice agents
• Backed by Peak XV, Bessemer, Kleiner Perkins, M12, Y Combinator, and more with $72M raised
• Try talking to Vapi now!

Why We’re Hiring This Role

The StreamModule pipeline — VAD → STT → LLM → TTS → Transport — runs on cork/uncork backpressure during live phone calls. A hundred milliseconds of delay is audible. This role owns pipeline stability and pluggability, so the agents and FDE teams can add new models and providers without touching core.

You’ll consolidate BullMQ into Kafka, harden the provider abstractions (LLM, STT, TTS base classes), instrument the pipeline with event-driven OTEL tracing, and shore up the Postgres SPOFs that contributed to the Oct 15 and Oct 22 incidents.

What You’ll Do

30 Day

Ramp on the StreamModule pipeline and the cork/uncork backpressure model. Walk the Oct 15 / Oct 22 DB incidents and the duplicate-message incident. Land a scoped pipeline or provider-abstraction improvement.

60 Day

Own a slice of the BullMQ → Kafka consolidation. Ship event-driven OTEL instrumentation for at least one critical pipeline stage. Harden one provider plugin path so a new model can be added without core changes.

90 Day

Drive a measurable reliability or latency win on the call path. Be the backend owner that agents and FDE teams pull in for design reviews on new providers and pipeline changes.

Who You Are

Must-haves

• You’ve built real-time or streaming systems in production — media pipelines, streaming data, or event-driven backends. You’ve debugged a backpressure cascade.
• You have opinions on queue architecture (BullMQ, Kafka, Temporal) and when each is the right fit.
• You’ve built plugin or adapter architectures — extending base classes cleanly, with decoupled implementations.
• You’ve operated Postgres at scale: connection pooling, read replicas, schema migrations (Liquibase or similar).
• You instrument with OpenTelemetry and think in event-driven traces, not just logs.

Nice-to-haves

• TypeScript + Node.js + NestJS. The codebase is huge NestJS, but a strong systems-thinking engineer ramps fast — language doesn’t gate the hire.

Tech stack you’ll work in

• Languages: TypeScript on Node.js (primary).
• Framework: NestJS (large codebase).
• Pipeline: StreamModule (VAD → STT → LLM → TTS → Transport), cork/uncork backpressure.
• Queues: BullMQ (current), Kafka (target — consolidation on roadmap), Temporal.
• Database: Postgres (connection pooling, read replicas), Liquibase for schema migrations.
• Plugin system: provider abstractions — LLM, STT, TTS base classes (pluggable, decoupled from model integrations).
• Observability: OpenTelemetry tracing, event-driven instrumentation.

Where you likely come from

A streaming or real-time platform (Discord, Slack, Zoom, Twitch, Mux, LiveKit), an ML-infra company (Modal, Baseten, Replicate, Together), or a pipeline/workflow shop (Temporal, Stripe Radar, trading systems).

Weak fit

backend engineer who’s only built systems where users don’t wait in real time (overnight jobs, reports, dashboards).

Why Vapi

Generational impact

Build the human interface for every business

Ownership culture

70% of the company are previous founders

Kind team

The founders, Jordan and Nikhil, are Canadians

Tier-1 Investors

YC, KP seed, Bessemer Series A, Recent Series B raise

What We Offer

Real stake

We offer a competitive salary and excellent equity ownership

Comprehensive health coverage

medical, dental, and vision plans

Team love

We love hanging out, and we do quarterly off-sites

Flexible time off

take what you need

More

catered meals, transportation, gym, and a $10k annual L&D budget