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 take pride in our diverse and talented team and partners, spread across the UK, Cyprus, the Netherlands, and other regions worldwide.

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).