Back End Developer Engineer in London

Pelago is the world's leading virtual clinic for Substance Use Management. From unhealthy habits to active substance use disorders, Pelago delivers a personalized solution based on individual health, habits, genetics, and goals, providing care for members wherever they might be on the substance use spectrum. Pelago's suite of virtual services ranges from education to cognitive behavioral therapy (CBT) to comprehensive medication-assisted treatment (MAT). Pelago enables employers and health plans to deliver accessible, affordable, and effective treatment for substance misuse. Pelago has scaled to helping hundreds of employers and health plans and has already helped more than 750,000 members manage their substance use better. If you are passionate about making an impact on the health of others, join us and make it happen!

About Pelago Engineering: Our engineering team operates as empowered, outcome-oriented problem solvers, working in close partnership with product, design, and clinical teams to improve member outcomes at scale. As AI transforms how software is built, we are intentionally evolving our development lifecycle so we spend less time on mechanical implementation and more time on system design, judgment, and impact.

AI-native: We use AI across the SDLC to accelerate implementation, testing, and review. With autonomy comes responsibility for quality, safety, and results. Engineers partner deeply with Product, Design, Data, and Clinical. Quality and safety matter: Design and evolve systems that support safe, scalable, AI-augmented development. Use data and experimentation to validate whether solutions actually work. You use AI to amplify your judgment and move faster on what matters. You want to own outcomes, not just ship features.

As a Backend Engineer, you'll play a critical role in building and scaling the backend systems that power Pelago's core services. You'll design and implement robust APIs, maintain our serverless AWS infrastructure, and work with complex data systems to ensure reliability, performance, and scalability. You'll collaborate closely with engineers, product managers, and other stakeholders, contributing to an event-driven architecture and taking ownership of mission-critical features from concept to deployment. This role is based in our London office, with in-person collaboration two days per week.

• Maintain and evolve our entirely serverless AWS-based architecture using Node.js and TypeScript.
• Contribute to the development of an event-driven system, owning core feature implementation and refactoring critical functionality as needed.
• Design and optimize MySQL databases at scale, including schema design and query performance improvements.
• Implement best practices for code quality, testing, and deployment automation in a collaborative agile environment.

Requirements:

• 4+ years of professional experience as a backend engineer.
• Experience with JavaScript and TypeScript.
• Years of working with SQL, including schema design, optimization, and scaling.
• Strong AWS expertise, including API Gateway, SNS, SQS, Lambda, Cognito, EC2, RDS, S3, CloudWatch, and VPC.
• Genuine curiosity about emerging technologies, including AI, and a proactive mindset toward exploring how they can enhance work, problem-solving, and innovation at Pelago.
• Familiarity with testing frameworks and experience writing unit and integration tests.
• Based in London or within commuting distance (2 days/week in-office).
• Experience with NoSQL databases.
• Experience scaling AWS environments in high-growth contexts.

Benefits:

• Private Health Coverage
• Pension Plan
• Unlimited PTO Policy, Bank Holidays, & company-wide 'Me Time Days'
• Paid maternity, paternity, & new parent leave
• Flexible working environment
• Annual Learning and Development stipend to support continued learning and career development
• Wellness Reimbursement Program
• Access to Reproductive & Family Planning Care