luna is live in over 170 countries, with 40k active users and a product teens and parents genuinely love. We’ve also partnered with some of the world’s leading health and fitness brands, including Adidas, Gymshark and Lil-Lets (and have a super exciting pipeline for 2026!).

We're female-founded, mission-driven, and looking for a Senior Engineer to join our incredible team and shape what comes next.

What you'll do

• We have a live React Native app on Firebase/GCP with 40k monthly active users. What we need now is velocity and the ability to run experiments fast, learn from data, and iterate toward product-market fit.
• You'll own the technical side: building the infrastructure to ship and measure experiments weekly, not monthly. You'll shape how we use AI as the product evolves. You'll mentor our mid-level engineer and build engineering culture from the ground up.
• You'll work side-by-side with our founders, supported by our fractional CTO, on the decisions that shape the product.
• This isn't a role where you inherit a team and maintain what exists. It's a role where you build and define what comes next.

What we're looking for

• React Native expertise. You've shipped production apps and understand RN architecture deeply.
• Backend fluency. You can own and evolve Firebase/GCP infrastructure. Cloud Functions, Firestore, Auth - you understand how to build systems that are reliable, observable, and secure.
• Product instinct. You care about our members. You push back on specs that don't make sense and propose better solutions.
• Mentorship mindset. You enjoy helping other engineers grow. You're someone who pairs generously, gives feedback that teaches, and gets satisfaction from watching another engineer level up.
• Ambition: You want to build the number 1 app for teens and you have the drive and grit to make this happen; you’re not afraid to think big.
• No-nonsense approach: You get things done and you’re not afraid to roll up your sleeves.
• Team player: We’re an early-stage startup, we win and learn together, with a strong sense of shared ownership and accountability.

What would make you exceptional

• LLM/AI implementation experience. RAG pipelines, vector stores, prompt engineering in production. We're building AI features and need someone who understands the practical realities.
• Growth engineering mindset. You think about CAC, LTV, activation, retention and know how technical choices affect them.
• Experience with teen/consumer audiences. You understand the unique responsibilities of building for young users: privacy, safety, trust.

Why this role

• Real ownership from day one.
• Shaping the engineering team as we grow with a path toward senior technical leadership as the company scales.
• Mission-led business with huge growth potential - we’re building in a white space and the work is truly meaningful (just read our App store reviews to check it out firsthand!)
• Join a team that works very hard, but plays hard too - we enjoy a bit of fun at luna!

Benefits

• 36 days holiday (including UK bank holidays)
• Learning and development budget
• Real influence on shaping how we work and grow as a company
• Flexible working. We work from home and from a shared office space

How to apply:

Please email john@weareluna.app with the following:

• Your CV
• A link to any of your publicly available code
• A short note outlining why this role excites you and how your experience and strengths align with what we’re looking for

Please note we are ready to interview asap!