FullStack Engineer

Title: FullStack Engineer Location: Europe SENIOR FULL-STACK ENGINEER — BACKEND LEANING (LARAVEL + REACT) Location: Remote within Europe Preferred locations: Czech Republic, Ukraine, Poland, or the UK Contract rate: Up to $60 USD/hour Core stack: PHP, Laravel, React, Inertia.js ABOUT THE COMPANY Our client builds APIs and developer tools for businesses working with creators. The company is profitable, growing quickly, and developing a unified API that allows customers to integrate with multiple creator and social platforms through consistent responses, webhooks, and SDKs. The engineering team works with high-volume background processing, third-party platforms that can change without warning, and customer data that must remain accurate and reliable. THE ROLE We are looking for a senior full-stack engineer with a strong backend focus. You will build and maintain production systems in Laravel and PHP while contributing to customer-facing features in React. This role is best suited to someone who enjoys investigating difficult production problems, building reliable integrations, and taking ownership in a small, highly autonomous team. You do not need to have operated exactly 50 million jobs per day. However, you should be able to explain the systems you have owned, how they failed, and how you measured and improved their limits. WHAT YOU’LL DO - Build and maintain production applications using Laravel, PHP, React, and Inertia. - Investigate production issues through logs, metrics, request flows, and queue behavior. - Design reliable queues, workers, and webhook-delivery systems. - Handle retries, duplicate execution, rate limits, backpressure, worker failures, and slow upstream services. - Build and maintain integrations with external and sometimes undocumented APIs. - Reverse engineer web or API behavior related to authentication, cookies, headers, request signing, rate limits, and other platform controls. - Create consistent API behavior across multiple creator and social platforms. - Improve database queries, worker capacity, job scheduling, and backend performance using measurable evidence. - Build customer-facing dashboards and internal tools with accurate, clearly presented data. - Add automated tests for critical failure scenarios and previously identified production issues. - Keep API documentation, SDKs, and developer tools aligned with production behavior. - Independently investigate problems, communicate blockers, and contribute to technical decisions. WHAT WE’RE LOOKING FOR - Strong professional experience building and maintaining production applications with PHP and Laravel. - Practical React experience and the ability to deliver full-stack product features. - Experience operating queues, workers, asynchronous jobs, or event-driven systems in production. - Good understanding of concurrency, retries, idempotency, duplicate execution, backpressure, and rate limiting. - Experience building and maintaining APIs and third-party integrations. - Strong production-debugging skills, including the ability to explain how you identified and verified the cause of an incident. - Experience with meaningful production volume or technically demanding backend workloads. - Ability to verify that application data represents the correct product behavior, including distinguishing missing data, failed requests, and legitimate zero values. - Strong ownership, independent judgment, and comfort working without every requirement being defined upfront. - Regular use of AI development tools, combined with the ability to validate generated code and explain what you ship. - Professional English communication. - Based in Europe and able to work remotely as an independent contractor. NICE TO HAVE - Experience reverse engineering undocumented APIs or web clients. - Experience with proxy infrastructure, bot detection, request signing, cookies, or TLS fingerprints. - Knowledge of OpenAPI, published SDKs, or MCP tools. - Experience with creator platforms, social media APIs, or adjacent products. - Experience with security testing or API abuse prevention. - Experience with PostHog. - Inertia.js experience. - Strong personal projects, public code, open-source contributions, or independently launched products. HOW THE TEAM WORKS This is a small, asynchronous team that reviews progress weekly. Engineers are expected to keep others informed about decisions, blockers, and incidents. Production reliability and correct customer data take priority. Working-hour overlap, incident coverage, response expectations, and any on-call arrangements will be discussed before an offer. INTERVIEW PROCESS - A practical debugging exercise that can be completed using AI tools. - A 30-minute technical walkthrough of your solution and decisions. - Final decision. The full process typically takes less than two weeks. The exercise takes approximately six to seven hours, including setup.