Senior Full Stack Engineer, Client Platform
The Client Platform team's job is to make product teams fast. The team owns the shared component libraries and design system, the build and release tooling every engineer touches daily, and the performance, accessibility, and observability standards that hold across client surfaces. Much of the work is internal tooling that keeps a large monorepo pleasant to work in. The team partners closely with product teams to make the right thing the easy thing.
The team also builds the server-driven UI service, a TypeScript GraphQL subgraph that lets product teams change what the iOS, Android, and web clients render without shipping an app release. The role spans both the monorepo and that service, so it is a genuine mix of front-end and backend GraphQL work.
- Design and evolve GraphQL schemas in a federated graph, including the server-driven UI contracts our mobile and web clients render.
- Treat those schemas as a versioned contract shared with released mobile apps: classify breaking changes, coordinate migrations with the iOS, Android, and web leads, and keep generated client models in sync.
- Develop, scale, and optimize the GraphQL APIs, RPC endpoints, and SQL queries behind our web surfaces.
- Build front-end applications and shared libraries with React and TypeScript.
- Build web applications that are fast and accessible to everyone.
- Partner with product and design to architect and ship customer-facing features.
- Use observability tooling to diagnose issues and improve the experience for guests.
- Set up and refine monitoring and alerting in DataDog for the systems you own.
- Improve code quality by finding technical debt, proposing fixes, and holding the standard for the whole team.
- Find bottlenecks and areas of risk in production, and drive the changes that make the platform scale.
- Learn from and mentor teammates through code review, pairing, and writing things down.
- Take part in the design, architecture, and delivery of new features in a collaborative agile team.
- Write thorough tests for every feature and bug fix. Testing is a first-class discipline on this team.
- Work with QA to strengthen automated testing pipelines and CI/CD workflows.
- Use Claude Code in daily development to move faster without lowering the bar.
- Other duties as required.
- At least 5 years of experience in software engineering (required).
- Strong JavaScript, TypeScript, and React, plus real instincts for UX (required).
- 2+ years designing and evolving GraphQL schemas for product surfaces used by multiple clients (iOS, Android, web) (required).
- Fluency with HTML, CSS, and the browser environment: DOM, events, platform APIs (required).
- A solid foundation in computer science, with strong competencies in data structures, distributed systems, algorithms, and software design (required).
- A grasp of production systems at scale, including finding weak points through load testing and tracing (required).
- Experience investigating and fixing production performance regressions, including CPU hotspots and latency in high-throughput services (required).
- Experience on an on-call rotation for a production service, and owning release cycles end to end (required).
- Clear writing. You have authored tech specs, runbooks, and cross-team design docs that stood up to scrutiny (required).
- Experience with API development in Node or Bun, or in another server framework (Phoenix, Ruby on Rails, FastAPI, Laravel) (required).
- Experience building and integrating multi-client or white-label platforms, including geo-based routing and per-brand configuration (required).
- Experience with Kubernetes and comfort operating services in containers (required).
- Comfortable working in the terminal, with Git and GitHub or similar, and in an editor of your choice (required).
- Experience with testing frameworks: Jest or Vitest, and ExUnit, RSpec, or pytest (required).
- Apollo Federation at scale (nice-to-have).
- GraphQL APIs with Absinthe (nice-to-have).
- Mobile Development for iOS or Android using Swift or Kotlin (nice-to-have).
- Hexagonal architecture (nice-to-have).
- Domain-driven design (nice-to-have).
- Relational databases (PostgreSQL, MySQL) (nice-to-have).
- Background job processing (Oban, Exq, Sidekiq, Celery) (nice-to-have).
- Asynchronous event infrastructure (Kafka, RabbitMQ, SQS/SNS, Pub/Sub) (nice-to-have).
- Open source contributions (nice-to-have).
- Startup experience (nice-to-have).
- Passion for sports or esports (nice-to-have).
- Competitive compensation package
- Fun, relaxed work environment
- Education and conference reimbursements
- Opportunities for career progression and mentoring others
Penn Interactive is the online gaming arm of PENN Entertainment, one of the largest regional casino operators in the United States. Headquartered in Philadelphia, it runs PENN's digital sports betting and online casino products, including theScore Bet and the Hollywood Casino online brands. The business previously operated the ESPN Bet sportsbook under a partnership with ESPN, which ended in late 2025. Penn Interactive combines proprietary technology - including theScore media platform - with PENN's nationwide casino network across North America.