Full Stack Developer, scalr

£40-60k

+ Equity

React

MongoDB

AWS

Node.js

Mid and Senior level

London

4-5 days a week in office (Holborn, London)

Behavioural analytics for gyms and fitness studios

Be an early applicant

Behavioural analytics for gyms and fitness studios

1-20 employees

B2BAnalyticsFitnessSaaS

Be an early applicant

£40-60k

+ Equity

React

MongoDB

AWS

Node.js

Mid and Senior level

London

4-5 days a week in office (Holborn, London)

1-20 employees

B2BAnalyticsFitnessSaaS

Company mission

To create healthy habits within communities around the world.

Job

Company

Role

Who you are

You’re a visionary doer—someone who thrives in high-growth environments and wants to build something meaningful from the ground up. You’re not just writing code; you’re designing systems that help gyms keep their members hitting the studio, week after week. You speak fluently across front-end, back-end, data pipelines, and cloud infra, but you pivot fast from spinning up a serverless AWS function to polishing a React UX component
You’re passionate about behavioural science: you believe data-driven nudges and algorithmic insights can re-ignite someone’s motivation just at the moment it starts to slip. You love tackling ambiguity, shaping best practices, and building the pipelines, APIs, and realtime integrations that empower operators to act—whether it’s engaging a struggling trialist or predicting a churn risk. You’re collaborative, detail-obsessed, and know how to elevate a team—mentoring juniors, leading by example, and delivering scalable, secure, production-ready systems fast

What the job involves

Own the full stack – from backend APIs and serverless AWS pipelines to React-powered components
Drive integrations with core systems (Twilio, WhatsApp, Mindbody etc) and spearhead new ones
Architect cloud-native architectures – scalable, fault-tolerant, secure—ready to power millions of gym-goers and hundreds of studios
Collaborate with Data Science to embed ML-driven models in production—surface predictive insights and automate outreach at scale
Elevate engineering standards – design CI/CD pipelines, containerised microservices (Docker), code reviews, observability, and automation
Shape product and culture – influence the roadmap, delivering behavioural-first design, and build systems that mean studios and members feel cared for
Celebrate real-world impact – watch operators double trial-to-member conversions, boost retention in under 4 months, and build healthier communities

Salary benchmarks

Our take

Like with much of the service industry, gyms and fitness studios spend countless hours formulating customer retention strategies, taking them away from day-to-day tasks. Scalr is a behavioural analytics solution for the fitness industry, helping brick-and-mortar fitness businesses to predict their customers' behaviour and act accordingly.

Working off research suggesting that membership cancellations are a result of gradually declining habits and motivation, Scalr helps its customers track red flag patterns in their gym users and then rebuild their enjoyment and fulfilment. Sustainable fitness routines and member longevity are at the heart of Scalr’s software, and with the gym industry booming, there’s plenty of potential for Scalr to grow its customer base.

Freddie

Company Specialist at Welcome to the Jungle

Company

Company HQ

Westminster, London, UK

Leadership

Noas Saghir

(Co-Founder)

Noas, an astrophysicist with a decade in behavioural causality, has applied his expertise to decode patterns and predict outcomes in public and private investment markets.

Michael Theodore

(Co-Founder)

Michael brings a decade of commercial leadership and personal insight, having seen firsthand at Uber and Cloud Kitchens how gyms lack tools to keep members engaged and reduce churn.

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