Software Engineer (Full-Stack) (Shopify) in Sheffield

About Flare

Flare is the number one delivery date platform for Shopify Plus brands globally. We power the delivery experience at checkout for over 700 merchants, handling the logic, rules, and complexity behind the scenes so shoppers always see accurate, reliable delivery options when it matters most.

We’ve grown 10x in revenue since Q1 2025, processing over $100M in orders annually across hundreds of thousands of checkouts every month. We’re growing at 15% month-on-month, cash-flow positive, and just getting started.

We’re building Flare into the end-to-end shipping logic layer for Shopify, from checkout UI to carrier integrations. Legacy and unreliable software owns this space today. We’re taking it from them.

Why this role exists

Flare was built by two founders. You’d be the third person in the company and the first engineering hire to join the founding team. The work is hard: real-time delivery calculation, geo and postcode rule enforcement, carrier and fulfilment integrations, checkout performance at scale. We need someone who loves building reliable systems fast and is happy to roll up their sleeves and get stuck in, whether that’s shipping a customer-facing fix that drives retention or architecting something that scales to ten times the load.

We move fast and the bar is high. You’ll work directly with our CTO, who built a rules and conditions engine from scratch that processes over a million requests a week, returning complex delivery decisions to Shopify in under 190ms. You’ll learn how those decisions got made, how to build for scale whilst shipping fast, and how to take something from zero to one. Our CEO grew Flare from nothing to 700 brands without a sales team, so when you’re building, you’re building on top of real commercial momentum.

You’ll own how you build, ship things live for major brands within your first weeks, and be pushed to do the best work of your career. If you’re the kind of engineer who finds that energising, this is the right place.

We’re an AI-first team. Using tools like Cursor and Claude Code isn’t optional - it’s how we move fast without cutting corners. Anything that helps us ship better product faster is fair game.

What you’ll work on

• The decision engine: At the core of Flare is a system that takes everything - postcode, product, carrier, cut-off time, cart, customer location - and distils it into a simple, accurate response that shows the right delivery options to the right shopper at the right moment. You’ll expand the rules and conditions layer, add new carrier and fulfilment integrations, and push the performance envelope as request volume grows.
• Checkout and customer experience: The Shopify checkout is one of the most constrained and scrutinised environments in eCommerce. You’ll build the frontend layer that takes the output of our decision engine and turns it into a fast, polished experience that shoppers actually enjoy using.
• AI-assisted onboarding: You’ll work on using AI to make setup as frictionless as possible, including building agents that can complete configuration autonomously.
• Scale and reliability: We’re building toward $1bn in orders processed. You’ll be a core part of figuring that out. Every architectural decision comes back to one question: is this fast and reliable enough?

The kind of person we’re looking for

We want someone who is deeply curious about the problems our merchants face, happy to get stuck into the work that makes customers fall in love with the product, and capable of thinking bigger when it matters. You care about the customer, you understand eCommerce, and you bring your own thinking to the table.

That means:

• At least 3 years of strong full-stack experience, comfortable moving between frontend product work and backend systems.
• Real experience with Shopify APIs, eCommerce, logistics, or complex rule-based backend systems.
• You think carefully about performance and know what it means to build a system that has to respond in milliseconds.
• You write with production in mind: failure cases, edge cases, what happens when something breaks at 3am for a merchant processing thousands of orders a day.
• You ship fast without being reckless, and you know the difference between moving quickly and cutting corners.
• You use AI tooling as a natural part of how you work.

The stack

TypeScript, React (Preact), Remix, Node.js, GraphQL, AWS (ECS/EC2, DynamoDB), Shopify APIs and Webhooks.

The hiring process

• Intro call (30 mins) with the CTO about your background and the role.
• Technical deep dive (60 mins) on a real system design problem relevant to Flare.
• Founder conversation (30 mins) with the CEO about how you work and what you’re looking for.
• Offer

What we offer

25 days holiday plus your local public holidays. We start with a one month trial, followed by a six month contract, with a move to a permanent position for the right person. We move quickly for the right person.

How to apply

Email with the following:

• An overview of what you’ve built and shipped: production apps, side projects, systems you owned or played a significant part in.
• Your GitHub profile, portfolio, or any links to live work.
• A short note on why this role resonates with you.