Experienced JS Back-End Developer — Visual Challenge Solving Platform

Description We're looking for exceptional engineers with strong back-end fundamentals and proven experience building high-scale distributed systems to join us at Hola, where we offer a unique and widely used VPN service that serves millions of users around the world with a strong focus on privacy, performance, and innovation . In this role, you will solve hard engineering problems on a large-scale visual challenge solving platform that spans orchestration services, computer-vision inference, and cloud infrastructure. You will take full ownership of critical systems, from design to production, in a fast-paced and professional agile environment.  For more information about HolaVPN: https://hola.org/ Responsibilities End-to-end design, development and ownership of critical back-end services, from architecture to production. Participate in system design and architecture planning, for optimal software performance, scalability and reliability. Solve complex engineering problems: distributed state, concurrency, tail latency, fault tolerance and high-throughput pipelines. Debug production issues end-to-end across services: gRPC channel churn, DNS/ASG failover, Redis queue backpressure, worker saturation and memory fragmentation. Design and maintain solver logic for complex visual challenges: image grids, drag-and-drop, object detection and browser automation. Build and optimize pipelines integrating OpenAI reasoning, computer-vision inference, Redis Streams, MongoDB session tracking and S3 screenshot archival. Take on independent responsibilities, while contributing to the team's collective goals. Actively learn, adapt and stay up-to-date with the evolving tech landscape, including best practices. Requirements At least 3 years of hands-on experience in software development / engineering, with a strong focus on back-end systems. Strong engineering fundamentals: algorithms, data structures, concurrency, distributed systems and performance analysis. In-depth understanding of network protocols and security, including TCP/IP, DNS, HTTP, HTTPS, CORS, WebSockets and gRPC. Proficient in system design and architecture to ensure product functionality, performance, scalability, and reliability. Track record of debugging and fixing hard production issues across multiple services or languages. Fast learner, able to work independently and as a team player. Fluent in English, with excellent communication skills. *Fully remote position for candidates who are not located in Israel.