Senior Fullstack Engineer

About X-FLOW and Happy Color

X-FLOW, established in 2018, is a leading mobile game development company renowned for creating Happy Color, the world's most popular digital coloring book and a highly successful ad-driven mobile application. We pride ourselves on our diverse and talented team, with partners and employees spread across the UK, Cyprus, the Netherlands, and various other regions globally.

The Role: Senior Fullstack Engineer for Happy Color

We are actively seeking a Senior Fullstack Engineer to join our team, specifically contributing to our flagship project, Happy Color. This role offers a unique opportunity to impact a globally recognized product.

Key Responsibilities

• Design and develop robust RESTful APIs using PHP/Laravel to power our applications.
• Build high-performance frontend applications leveraging TypeScript/React, prioritizing an excellent Developer Experience (DX).
• Integrate seamlessly with external services, meticulously defining and maintaining API contracts.
• Proactively optimize application performance, conducting profiling, and significantly reducing latency.
• Design efficient database schemas, manage migrations, implement effective indexing, and optimize query performance using PostgreSQL/MySQL and Redis.
• Contribute significantly to quality assurance through writing comprehensive unit, integration, and end-to-end tests, conducting thorough code reviews, and automating checks.
• Ensure exceptional observability and reliability by implementing robust logging, metrics, alerts, and tracing solutions.
• Actively participate in the design and evolution of architectural solutions across our platforms.

Required Skills and Experience

• Backend Expertise: 4+ years of hands-on experience with PHP, demonstrating strong knowledge of Laravel, including Dependency Injection, queues, profiling, RESTful principles, and modularity.
• Frontend Prowess: 4+ years of experience with TypeScript, coupled with strong proficiency in React/Redux Toolkit, routing strategies, build processes, and bundle optimization.
• Database Proficiency: Proven experience with PostgreSQL/MySQL and Redis, covering schema design, indexing, and transactional integrity.
• Message Queuing: Practical experience with Kafka for event-driven integrations.
• Security Foundations: Solid understanding and application of OAuth2 and JWT.
• Architectural Principles: Familiarity with Domain-Driven Design (DDD), SOLID principles, 12-Factor App methodology, and observability concepts (Prometheus/Grafana, OpenTelemetry).

Nice-to-Have Qualifications

• Experience in Golang development.
• Development experience with Ant Design (Antd) 5+.
• Familiarity with or understanding of GitLab CI, feature flags, database migrations, and advanced deployment strategies like blue-green or rolling deployments.
• Proficiency with testing tools such as Jest, Playwright for frontend, and PHPUnit/Codeception for PHP, alongside general integration and end-to-end 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 at X-FLOW

• A competitive salary and comprehensive benefits package.
• The chance to collaborate with a talented and passionate team in a creative and dynamic environment.
• Flexible working hours and options for remote or office-based work.
• Significant career growth and professional development opportunities.
• A fun, inclusive company culture that celebrates diversity and fosters creativity.

Key skills/competency

• PHP
• Laravel
• TypeScript
• React
• RESTful APIs
• PostgreSQL
• Kafka
• Performance Optimization
• Observability
• System Architecture