Senior Backend Engineer

Fyxer AI; London; On-site; GBP 90,000 - 110,000; Full time

Job summary

Join a leading AI startup as a Senior Backend Engineer, working onsite in Central London. You will be integral to scaling our backend systems and building innovative tools that enhance productivity for professionals. Our ideal candidate has extensive experience in TypeScript and cloud technologies, thrives in a fast-paced environment, and is passionate about impactful tech.

Benefits

Equity in a high-growth startup

Huge ownership and autonomy

Work closely with an elite founding team

Opportunity to build impactful technology

Fast-paced startup environment with traction

Qualifications

• 4+ years experience as a backend engineer in a startup or high-growth environment.
• Expert-level fluency in TypeScript, including server-side development.
• Experience with AI or strong interest in AI-powered productivity tools.

Responsibilities

• Design and scale backend infrastructure to handle millions of user actions.
• Build real-time processing pipelines for email, calendar, and Zoom data.
• Collaborate on product direction, usage insights, and user experience.

Skills

TypeScript

Google Cloud Platform

SQL

Cloud Functions

CI/CD

Tools

GitHub Actions

BigQuery

Job description

This job is brought to you by Jobs/Redefined, the UK's leading over-50s age inclusive jobs board.

Help Us Build the Backend Powering One of Europe's Fastest-Growing AI Startups

Role: Senior Backend Engineer
Location: Onsite, Central London (Holborn), 4 days/week
Salary: £90k-£110k + meaningful equity
Reports to: Matt, Cofounder & CTO

What Are We Building?

Great people are working on overdrive to do a great job but are held back because their inbox is failing them.

We're building an AI productivity tool that eliminates admin for client-facing professionals: consultants, recruiters, real estate agents anyone drowning in emails, scheduling, and follow-ups. Fyxer AI drafts emails in your voice, takes crisp meeting notes, and auto-manages your inbox.
How's It Going?

Since launching in May 2024, we've grown from $0 to $10M+ ARR with thousands of paying users. In Feb 2025, we raised a $10M Series A backed by top-tier investors including Marc Benioff (Salesforce) and 20VC.

We spent Q4 2024 at HF0 in San Francisco, the top AI startup accelerator, learning from legends like the CEO of Instacart and the Head of Applied Research at OpenAI.

We're now entering hypergrowth and building the engineering team that will scale us to $50M+ in revenue.

What We Value

Small teams. Big ownership. High talent density.

We don't hire for headcount. We hire people who ship, who care, and who think from first principles.

At Fyxer, "Product Engineer" means you're not just writing backend endpoints you're building products. You'll look at usage data, talk to customers, and design elegant solutions with real impact.

What You'll Be Doing

You'll work closely with Matt (CTO) and the engineering team to scale and evolve our backend systems as we grow to tens of thousands of users.
Expect to own high-leverage features across everything from core architecture to AI workflows to observability.

Some things you'll work on:

• Design and scale backend infrastructure to handle millions of user actions per day
• Build real-time processing pipelines for email, calendar, and Zoom data
• Own integrations with external APIs (Google, Microsoft, OpenAI)
• Collaborate on product direction, usage insights, and user experience
• Drive performance, reliability, and observability across our cloud functions and services
• Make key decisions around architecture, data modelling, and tooling

Our Ideal Candidate

• 4+ years experience working as a backend engineer in a startup or high-growth environment
• Expert-level fluency in TypeScript, including server-side development
• Solid experience with Google Cloud Platform or similar (e.g. AWS, Azure)
• Built scalable systems using Cloud Functions, PubSub, Firestore, Cloud Storage, etc
• Confident writing SQL (BigQuery or equivalent) and building data flows that scale
• Comfortable owning infrastructure and CI/CD (we use GitHub Actions + GCP)
• Product mindset you care about what you're building and why it matters
• Experience with AI or high interest in AI-powered productivity tools would be ideal
• Intensity, urgency, and high standards for your work

Our Tech Stack

• TypeScript across the stack
• React frontend, but the product is backend-heavy
• Google Cloud Platform: Cloud Functions, Firestore, Cloud Storage, PubSub
• BigQuery, Looker, Sentry, Google Cloud Logging
• CI/CD via GitHub Actions

What You'll Get

• Salary + equity in a rocketship-stage startup
• Huge ownership and autonomy from day one
• Work in-person with an elite founding team (Oxford, HF0, backed by world-class investors)
• A chance to build category-defining tech that people actually use
• Early-stage speed with the scale and traction of a growth company

Application Process

• Submit your CV (no cover letter needed)
• 20-min intro call
• Live coding interview (45 mins)
• Backend/product case study (45 mins)
• Meet the team over lunch in our Holborn office