Senior Product Engineer (Elixir)

Location: London, UK; onsite or remote

Company

Cheerful Monster is a London development studio building AI systems for healthcare, government, and other regulated environments.

What you will do

• Work in a small pod directly with clients.
• Take projects from early ambiguity through design, implementation, and deployment to production outcomes.
• Build and maintain AI systems using Elixir, Phoenix, LiveView, and Ash.
• Use AI coding agents to explore codebases, plan work, implement features, generate tests, and review changes.
• Evaluate generated code and remain accountable for the quality of shipped software.
• Help establish engineering practices for future Bonfire teams.

Requirements

• Substantial production experience with Elixir and Phoenix.
• Strong understanding of OTP and relational data modelling.
• Ability to identify generated code that compiles but is incorrect.
• Strong product judgement and comfort working directly with clients.
• Clear technical writing skills.
• Experience as an AI-native developer or strong senior engineering fundamentals with readiness to retool.

Nice to have

• Experience with Oban, Broadway, distributed systems, data engineering, or Python.

Culture & Benefits

• Small-pod collaboration with direct client engagement.
• Real client work and close mentorship through the Bonfire programme.
• AI coding agents are part of the standard development environment.
• Opportunity to influence engineering practices inherited by future teams.