Sr. Full Stack Engineer

Location: Montreal

The opportunity  At Unity, we're building a world-class advertising platform that operates at a massive global scale.
The Ads team powers the systems that connect advertisers with creators and players, driving performance, reliability, and growth across our ecosystem.
As a Senior Full-Stack Engineer on the Unified Ads Platform team, you'll own the service layer where advertiser and publisher entities live.
Campaigns and budget caps, applications and ad units, creative packs and the moderation pipeline behind them, offerwall currency, A/B tests, Level Play integration.
These are the records the rest of the ads estate reads from, and our APIs are the source of truth for them across serving, billing, and reporting.
This role goes beyond building an API and moving on.
The data you model is consumed by systems you don't own, in paths where a wrong value costs money.
You'll design contracts that stay stable as the product changes, keep state consistent across service boundaries, and own the correctness and availability of all of it in production.
This role is ideal for someone strong on both sides of the stack who thinks in terms of data contracts and correctness, and who wants real ownership of systems other engineering teams depend on.
As the team grows, this role has a path to evolve into a Tech Lead Manager position.
What you'll be doing   Design, build, and operate services in our Type Script platform (NestJS) across a large domain model, owning the APIs and data contracts that downstream ads systems depend on
Model entity data for scale and change — relational schema design, migrations, and schema evolution against tables that serving, billing, and reporting all read from
Design and build event-driven integrations with Kafka and Google Cloud Pub/Sub, using patterns such as transactional outbox and idempotent consumers to maintain consistency across service boundaries
Deliver the user-facing surfaces on top of the platform in React and Type Script, turning dense entity and performance data into workflows publishers and advertisers can trust
Operate what you build on Kubernetes, where the service declares its own cloud infrastructure alongside its code, and take real ownership of its SLOs
Drive observability and quality across the platform — distributed tracing, metrics, and testing frameworks
Set the standards for how the service is built and hold the line on them in design and code review, mentoring engineers as you go
What we're looking for   6+ years building and operating production software, with real depth on both backend services and modern frontend
Advanced Type Script, and experience with an opinionated, modular Node backend framework — NestJS, or comparable dependency-injection and module architectures
Strong data modelling and SQL — schema design, migrations, and performance at scale, alongside the API versioning judgment that goes with it
You've had to change something other teams read from, safely
Event-driven systems — Kafka, Pub/Sub, or similar. You understand delivery semantics, ordering, and idempotency, and what happens when two systems disagree
Advanced React, with strong judgment around component design, state management, and performance in data-intensive interfaces
Cloud-native operation — containerized services on Kubernetes, and comfort owning the system in production, including deployment, scaling, monitoring, incident response, and on-call
Strong ownership mindset — focused on correctness, observability, and long-term maintainability, backed by real engineering discipline in testing, review, and accessibility
You might also have Background in ads, attribution, billing, or monetization systems
Infrastructure-as-code experience — Kubernetes-native resource management, Terraform, or…