Senior Software Engineer (SDE3)

SaaS Labs; Bengaluru; On-site; INR 3,500,000 - 5,500,000; Full time

Job summary

SaaS Labs is seeking a Senior Full-Stack Growth Engineer to own onboarding, activation flows, monetisation infrastructure, and experimentation systems. You will help scale JustCall as a flagship product across global customers, building growth engines at the intersection of engineering, product, and data.

Role focuses on end-to-end growth experiences, from backend services to frontend interfaces, with emphasis on reliability, analytics, and experiment-driven product improvements.

Qualifications

• 5+ years of software engineering experience with Node.js and TypeScript.
• Experience with NestJS and API design in production systems.
• Proficiency in MongoDB data modelling, indexing, and scalable backends.
• Experience building REST APIs and integrating services at scale.

Responsibilities

• Architect backend services using Node.js, NestJS, and TypeScript for scalable APIs.
• Design data systems with MongoDB for low latency and consistency at scale.
• Build growth workflows for onboarding, activation, subscriptions, and monetisation.
• Own end-to-end features from design through deployment and monitoring.

Skills

Node.js

TypeScript

NestJS

API design

Distributed systems

Backend architecture

Testing & reliability

Ownership

Tools

MongoDB

Job description

You'll be the first engineer dedicated to owning those critical paths: onboarding, activation flows, monetisation infrastructure, and the experimentation systems that help us improve all of it. As JustCall expands how it serves customers - from individual sales reps to small teams to mid-market organisations running AI-powered call workflows - you'll play a central role in building the growth engine that scales with them.

We're looking for a Senior Full-Stack Growth Engineer who is excited to build those journeys end-to-end. You'll work at the intersection of engineering, product, and data to create fast, reliable growth systems that turn first-time users into activated users, and activated users into expanding accounts.

What you'll actually do

• Architect backend services: Design and scale production-grade services using Node.js, NestJS, and TypeScript, with clean service boundaries, robust API contracts, and maintainable business logic.
• Build reliable data systems: Design MongoDB schemas, indexing strategies, and efficient query patterns; optimise latency, concurrency, and data consistency as the product scales.
• Engineer growth workflows: Build the systems powering onboarding, activation, subscription management, feature entitlements, trial conversion, and account expansion.
• Develop data-driven growth infrastructure: Integrate event instrumentation, ClickHouse analytics, feature flags, and experimentation to identify funnel friction and improve product conversion.
• Own full-stack product experiences: Build responsive React and Next.js interfaces, integrating them with backend APIs to deliver seamless onboarding, configuration, and upgrade journeys.
• Drive production reliability: Implement automated testing, observability, error handling, and resilient integrations; debug performance bottlenecks and resolve issues across the stack.
• Own features end-to-end: Drive technical design, implementation, code reviews, deployment, and optimisation while collaborating with Product, Design, and Data teams.

What we're looking for

• Strong backend fundamentals: 5+ years of software engineering experience, with substantial hands-on expertise in Node.js, TypeScript, NestJS, API design, and production backend systems.
• Database and systems expertise: Proficiency in data modelling, indexing, query optimisation, and consistency patterns, with experience in MongoDB and an understanding of distributed systems, caching, concurrency, and asynchronous processing.
• API and integration design: Experience building REST APIs and integrating third-party services, with sound handling of retries, idempotency, webhooks, rate limits, and failure recovery.
• Product and growth orientation: Ability to translate ambiguous product problems into scalable engineering solutions, ideally across SaaS onboarding, activation, subscriptions, monetisation, or self-serve growth.
• Data-driven engineering: Familiarity with event instrumentation, product analytics, and experimentation; experience with ClickHouse and GCP is a strong advantage.
• Ownership and engineering judgement: Proven ability to debug production issues, make architectural trade-offs, write meaningful automated tests, and own features from design through deployment and monitoring.

How we work

• Outcomes over process. We measure engineering impact by production reliability, latency benchmarks, eval coverage, and the AI experiences we ship - not tickets closed.
• Deeply hands-on culture - leadership here means staying close to the hardest technical problems, not delegating your way out of them.
• Fast cycles, high ambiguity, and the expectation that you bring both architectural depth and shipping velocity to every initiative.
• Competitive pay tied to the systems you architect and the engineering culture you build.

The bigger picture

JustCall is SaaS Labs' flagship product - used by 6,000+ businesses across 70+ countries to run their customer conversations. We're backed by Peak XV and Base10 Partners, have crossed $40M ARR, and are building toward $100M with the team, the product, and the infrastructure to get there.

SaaS Labs takes pride in being an equal opportunity employer. We believe diverse teams build better products, which is why we're committed to making hiring or any employment decision regardless of race, colour, religion, national origin, age, sex, marital status, ancestry, disability, genetic information, veteran status, gender identity, sexual orientation, or any other characteristic.