Backend Engineer in London

Pelago is the world’s leading virtual clinic for Substance Use Management. Our program provides guidance, support and treatment for members seeking to overcome their tobacco, alcohol and opioid use. 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. We have recently closed our Series C and raised over $151m from leading global investors. 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.

How We Work:

• Outcome-driven: Engineers are given problems to solve, not just features to build. Success is measured by learning, impact, and outcomes—not velocity alone.
• AI-native: We use AI across the SDLC to accelerate implementation, testing, and review. Engineers focus on defining intent, validating behavior, and designing resilient systems.
• High autonomy, high accountability: Teams have real ownership over their domains. With autonomy comes responsibility for quality, safety, and results.
• Cross-functional by default: Engineers partner deeply with Product, Design, Data, and Clinical. Discovery, experimentation, and delivery are shared responsibilities.
• Quality and safety matter: We build in a regulated, member-impacting domain. Reliability, observability, and correctness are first-class concerns.

What You’ll Do:

• Own meaningful problem spaces end-to-end, from discovery through delivery and iteration.
• Design and evolve systems that support safe, scalable, AI-augmented development.
• Use data and experimentation to validate whether solutions actually work.
• Collaborate cross-functionally to balance member impact, clinical constraints, and technical tradeoffs.
• Shape how we work—our tools, processes, and culture.

What We Look For:

• You start with 'why' before diving into 'how'.
• You’re energized by ambiguity and collaborative problem-shaping.
• You use AI to amplify your judgment and move faster on what matters.
• You think in systems and anticipate second-order effects.
• You want to own outcomes, not just ship features.

Overview of the Role: 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. Your work will directly support Pelago’s mission by enabling secure, scalable, and efficient systems that connect our members to the care they need. This role is based in our London office, with in-person collaboration two days per week.

In this role, you will:

• Build scalable, performant, secure, and well-tested APIs.
• 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.
• Manage and integrate third-party APIs, ensuring reliability, security, and maintainability.
• Implement best practices for code quality, testing, and deployment automation in a collaborative agile environment.
• Partner with cross-functional teams to translate business requirements into scalable technical solutions.

We’re Looking For You To Bring:

• 4+ years of professional experience as a backend engineer.
• Extensive experience with Node.js and TypeScript.
• Proven track record with event-driven architectures.
• 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.
• Experience integrating and managing third-party APIs in production environments.
• 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).

Nice to haves:

• Experience with NoSQL databases.
• Infrastructure provisioning using Terraform.
• Experience scaling AWS environments in high-growth contexts.
• Knowledge of serverless architecture trade-offs and benefits.
• API security best practices.

What You’ll Love About Us: We have a whole host of perks for our people! From life essentials to nice-to-haves, there are more than a few good reasons to love working with us. We strive to ensure Pelago employees have equitable access to healthcare, wellbeing, time away, and then some.

• Generous and meaningful equity package.
• 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.
• Substance Use Support for employees and family members.

At this time, we are unable to offer visa sponsorship for this position.

Before you apply, see how we build. We write about our technical decisions, product philosophy, and the real challenges of scaling behavioral health.