Senior Software Engineer Engineering · London · On-site

Wayfindi; Greater London; On-site; GBP 70,000 - 90,000; Full time

Job summary

Wayfindi is seeking an experienced backend engineer to own and ship core platform systems that power health data flow. You will design real-time systems, scale streaming data, and build APIs that enable developers to utilize health data effectively.

With a focus on speed and autonomy, you'll work across the entire stack, ensuring high performance and security. If you are passionate about health data and thrive in a fast-paced environment, we would love to hear from you!

Qualifications

• 5+ years of production backend engineering experience.
• Deep API design experience with external developers.
• Proficient in Python and/or Go.
• Strong with distributed systems and data pipelines.
• Security-first thinking and compliance with regulations.
• Ability to work autonomously and with high velocity.

Responsibilities

• Own and ship core platform systems for health data.
• Design and extend the systems for data ingestion.
• Scale real-time streaming infrastructure for live data.
• Build the authentication layer for developers and suppliers.
• Maintain high uptime and reliability of the platform.

Skills

Backend engineering

API design

Distributed systems

Proficiency in Python or Go

Database expertise

Cloud-native mindset

Security-first thinking

Autonomous and fast

Tools

PostgreSQL

Redis

AWS

GCP

Job description

we make it easy for developers and AIs to build on health data. hundreds of wearables, sensors, labs, and health apps — connected, normalized, and made intelligent through a single platform. 1,000s of developers and AI labs build on Terra today. we process 15+ billion health data events per year. and we are just getting started.

the health OS

health data is fragmented. every device, every app, every sensor speaks a different language. we built the health OS to solve that — a full-stack platform that turns raw, messy, siloed health data into something developers and AIs can reason over, build on, and ship with.

Terra was founded in 2021 and operates from London, San Francisco, and South Korea.
we are funded by Y Combinator (W21), General Catalyst, Samsung NEXT, NEXT Ventures, and many of the world's finest investors.

we are a team of engineers, researchers, builders, and designers. we hire people who get things done, think from first principles, and learn ferociously. we default to yes. we ship fast. we hack. we build. we don't do bureaucracy.

You will own and ship core platform systems that power how health data flows through Terra — from upstream data suppliers (wearables, health apps, sensors) into our unified schema, and out to downstream developers and AI consumers via our REST API, Streaming API, and webhooks.

This is not a maintenance role. You will build new data connectors, scale real-time streaming pipelines, harden our authentication layer, and design the systems that handle millions of API calls per day. You will work across the entire stack — from low-level data ingestion to developer-facing API surfaces.

You will ship fast, iterate through feedback loops, and think in first principles. We don't have layers of process. We have ownership and velocity.

What You Will Build

Unified API & Data Normalisation:Design and extend the systems that ingest raw health data from 100+ upstream providers (Garmin, Fitbit, Oura, Apple Health, Google Fit, Withings, etc.) and normalise it into Terra's standardised schema — consistent today, consistent next year.

Upstream Data Supplier Connector:Architect and build Terra's new upstream connector capability, allowing data suppliers to push data directly into the platform. Define ingestion contracts, enforce data quality SLAs, and ensure schema compliance.

Streaming API:Scale our real-time streaming infrastructure for live sensor data (heart rate, steps, distance) from Apple Watch and BLE/ANT+ devices via websocket listeners. Sub-second latency matters here.

Authentication & Developer Experience:Own the authentication layer for both upstream suppliers and downstream developers. Build the OAuth flows, API key management, and RBAC + least privilege access controls that keep 1,000+ developers secure.

Webhooks & Event Delivery:Design and harden the webhook delivery system that pushes health data events to downstream consumers. Guaranteed delivery. Retry logic. At-scale.

Teams API:Contribute to our Teams API — enabling coaches, researchers, and organisations to aggregate and analyse group data across athletes, patients, and study participants.

Health Scores & Derived Data:Build the backend systems that transform raw health metrics into validated scores (recovery, strain, stress, immunity) backed by research.

Infrastructure & Reliability:Maintain 99.5%+ uptime on a platform that processes billions of events. Design for fault tolerance, observability, and horizontal scale

What We Are Looking For

5+ years of production backend engineering.You have shipped systems that handle real traffic at scale. Not toy projects — real, battle-tested infrastructure.

Deep API design experience.You've built REST APIs consumed by external developers. You understand versioning, rate limiting, pagination, error handling, and what it takes to make a developer love your API.

Strong with distributed systems.Message queues, event-driven architectures, stream processing, data pipelines — you've built and operated them.

Proficiency in Python and/or Go.Our stack is opinionated. You should be deeply fluent in at least one.

Database expertise.PostgreSQL, Redis, time-series stores. You know when to use what and how to make it fast.

Cloud-native mindset.AWS/GCP. Containers. CI/CD. Infrastructure as code. You don't wait for DevOps — you are DevOps.

Security-first thinking.Encryption in transit and at rest (TLS 1.2+, AES-256). Data minimisation. GDPR, HIPAA, SOC 2 are not afterthoughts — they're built in from the start.

Autonomous and fast.You don't need to be told what to do. You see the problem, you own it, you ship the fix. High velocity, high standards.

You are an athlete.You train, you compete, you push limits — or at the very least, you are obsessed with quantifying your own data. The discipline, ambition, and courage it takes to show up every day and get better is the same energy we run on. If you understand the data because you live it, you'll build a better product.

How we work

We are a high-velocity team. We think in first principles, build via feedback loops, and default to "yes." When someone says something is hard, we focus on how to build it, not whether to.

Skin in the Game.Everyone has equity. Everyone has stake. Your work directly moves the platform.

Deep Work.We protect focus time. No meeting culture. We ship, not talk.

Antifragile.We get stronger from chaos. Incidents make us better. Feedback makes us faster.

Resourceful.We don't wait for perfect conditions. We build with what we have and iterate relentlessly.

Hackers.We've battled at HackMIT, TreeHacks, and Harvard Hack. We build because we can't stop building.

By submitting this application, I agree that my personal data will be collected, processed, and retained by the company solely for the purposes of managing and assessing my candidacy.