Senior Fullstack Engineer
X-FLOW · Warsaw, Mazowieckie, Poland
About this role
The Senior Fullstack Engineer will work on the flagship project Happy Color, a highly successful mobile game development company. The role involves designing and developing RESTful APIs using PHP/Laravel and building frontend applications with TypeScript/React. Key respons'sibilities include database schema design, performance optimization, and ensuring observability and reliability through logs, metrics, and traces. The engineer will work within a technology stack including PostgreSQL/MySQL, Redis, Kafka, and Clickhouse, utilizing GitLab CI and Docker for DevOps. The position offers flexible working hours and remote or office work options.
Skills & technologies
Must have
- PHP
- Laravel
- TypeScript
- React
- Redux Toolkit
- PostgreSQL
- MySQL
- Redis
- Kafka
- OAuth2
- JWT
- DDD
- SOLID
- 12-Factor App
- Prometheus
- Grafana
- OpenTelemetry
- Docker
- GitLab CI
Nice to have
- Golang
- Ant Design
- GitLab CI
- Jest
- Playwright
- PHPUnit
- Codeception
Read full description
X-FLOW is a mobile game development company established in 2018. We gained recognition after the release of Happy Color, the most popular digital coloring book and one of the most successful ad-driven mobile apps in the world.
We are currently looking for a Senior Fullstack Engineer for our flagship project, Happy Color.
Key Responsibilities:
- Design and develop RESTful APIs using PHP/Laravel.
- Build frontend applications using TypeScript/React with a focus on performance and Developer Experience (DX).
- Integrate with external services; define and maintain API contracts.
- Optimize performance, perform profiling, and reduce latency.
- Design database schemas, handle migrations, indexing, and query optimization.
- Contribute to quality assurance: write tests (unit/integration/e2e), conduct code reviews, and automate checks.
- Ensure observability and reliability: implement logs, metrics, alerts, and traces.
- Participate in designing architectural solutions.
Requirements:
- 4+ years of experience with PHP, strong knowledge of Laravel (DI, queues, profiling, REST, modularity).
- 4+ years of experience with TypeScript, strong knowledge of React/Redux Toolkit, routing, build processes, and bundle optimization.
- Databases: PostgreSQL/MySQL, Redis; experience with schema design, indexes, and transactions.
- Message Queues/Buses: Kafka — experience with event-driven integrations.
- Security: OAuth2, JWT.
- Understanding of DDD, SOLID, 12-Factor App methodology, and observability (Prometheus/Grafana, OpenTelemetry).
Nice to have:
- Experience with Golang development.
- Development experience with Ant Design (Antd)
- 5+.Experience with or understanding of GitLab CI, feature flags, migrations, and blue-green/rolling deployment strategies.
- Testing tools: Jest, Playwright; for PHP — PHPUnit/Codeception; integration/e2e testing experience.
Technology Stack (Core):
- Backend: PHP (Laravel), REST, PostgreSQL/MySQL, Redis, Kafka, Clickhouse.
- Frontend: TypeScript, React, Redux Toolkit.
- DevOps: GitLab CI, Docker.
- Observability: Prometheus, Grafana, OpenTelemetry, Sentry.
What We Offer:
- Competitive salary and benefits package.
- Opportunity to work with a talented and passionate team in a creative and dynamic environment.
- Flexible working hours and remote/office work options.
- Career growth and professional development opportunities.
- A fun and inclusive company culture that celebrates diversity and creativity.
Join us and let’s create great product together!
