Backend Engineer (Go)

About Prelude

Prelude is redefining how companies onboard and authenticate users in a world where trust, speed, and conversion matter more than ever.

We help businesses verify users with less friction, higher security, and better economics, turning authentication from a cost center into a growth lever. Our flagship product enables companies to send OTP codes with the best price to conversion ratio on the market, dynamically selecting the most effective delivery channel in real time, from optimized SMS routing to messaging apps like WhatsApp. At the same time, Prelude actively blocks spam and fraud patterns that legacy providers routinely miss, protecting margins and user experience.

Founded in 2022 and backed by leading venture capital firms, Prelude has quickly reached strong product market fit and healthy financials, serving fast growing companies across Europe and expanding into the US market. Authentication is only the starting point.

With an ambitious roadmap and a pipeline of market defining products, we are building the platform for trust at scale, empowering companies to onboard users seamlessly, fight fraud intelligently, and grow globally with confidence.

About the team

Prelude was founded by former Zenly team members who experienced firsthand the limitations of existing authentication solutions. While building products used by millions, we saw how SMS authentication had become expensive, unreliable, and vulnerable to spam and fraud, ultimately leading to the creation of Prelude.

Today, we are a team of 40 and growing, based in Paris, building products that power secure and high-performance user onboarding for companies across Europe and the US. We believe small, highly skilled teams outperform large, fragmented organizations, and we are intentional about staying focused on impact, quality, and speed.

We operate with a flat organizational structure and value in-person collaboration, which helps ideas move faster, decisions stay grounded, and teams take full ownership of what they build.

Our values shape how we work every day:

• Care
  We care deeply about our customers, our teammates, and the quality and reliability of what we ship.

• Bias for Action
  We move fast, test in the real world, and iterate quickly rather than over-optimizing in theory.

• Ownership
  We take responsibility end to end, from identifying problems to delivering outcomes and learning from results.

These values underpin the company we are today and the team we are building for the future.

What will you be doing?

• Building and scaling a distributed system using Go, DynamoDB, SQS, Redshift and Lambdas

• Building a snappy full-stack app using cutting-edge tech (including Next on Vercel, gRPC)

• Working on the next version of the Prelude API, which we strive to be industry-leading in terms of usability, performance and functionality

• Ensuring that our services are scalable, extensible, reliable, and performant

• Helping deploy and scale our fraud prevention model to hundreds of large customers

• Developing and maintaining internal tools to improve developer efficiency

• Interacting with clients on a daily basis to assist them and build features around their needs

• Participating in on-call rotations to guarantee the stability and reliability of our APIs

What are we looking for?

• Years of experience designing and engineering large-scale systems

• Strong coding skills in Go - any experience with Rust, TypeScript or similar is a huge plus

• A preference for simplicity vs complexity, with intuition for what will scale effectively

• A product led mindset, keen to code for the output and the impact

• Fluent/professional English given our international team

• Any experience building frontends with modern frameworks like React or Vue is another huge plus

What can we offer you?

• Competitive compensation package with BSPCEs

• 4 days in-office in central Paris, with 1 days WFH; and 4 weeks of remote work per year

• 100% travel to the office subsidised

• Health insurance via Alan

• Urban Sports Club gym membership

• We will provide you with the gear you need for your role (a laptop and a phone, for on-call rotations)

• Swile meal vouchers

• Free snacks and drinks in the office

• An annual offsite in a great location (last one was at La Pradet!)

• The opportunity to build something from 0-1, and make an impact every day

Interview process

• Meet a member of the Talent team

• Technical assessment

• In person interview (system design, coding)

• Final meeting with CEO

We don't expect you to ace all these stages, we will evaluate your creativity and how you approach difficult problems. You should consider applying even if you don't meet all the criteria.