Senior Backend Engineer - Growth Pillar (FR)

WeWard SAS; Paris; Hybride; EUR 90 000 - 140 000; Plein temps

Avantages offerts par ce poste

Hybrid work 2 days remote per week

Learning & development budget

Central Paris office with perks

Résumé du poste

WeWard SAS is seeking a Senior Backend Engineer to join the Growth Squad in Paris. You will design, develop, test, and deploy APIs and backend processing with a strong ownership mindset, and lead the evolution of Echo for scalable campaigns. You’ll collaborate with PMs to scope work and mentor junior engineers.

The role sits in a hybrid setup, with two remote days per week, in a company focused on movement, rewards, and wellness across global markets.

Qualifications

• 6+ years of experience as a Backend Engineer.
• Experience with large-scale, high-traffic systems.
• Interest in startup world and health/wellness sector.
• International environment experience or openness is a plus.

Responsabilités

• Design, develop, test, and deploy APIs and backend processing with ownership over what you build.
• Lead the evolution of Echo and related campaign platforms at scale.
• Collaborate with PMs to assess feasibility and plan delivery; mentor engineers.

Connaissances

Backend Engineering

Large-scale systems

Ownership

Agility

Outils

Python

Flask

FastAPI

Description du poste

Hi there!

About us

WeWard is the app that rewards you for walking and turns everyday steps into real-life rewards, connections, & positive impact!

Our mission is help people move more, feel better, and make movement meaningful.

Today, we are trusted by 30M+ users worldwide, with a fast-growing, international team and offices in Paris and New York.

Our ambition is to build the world’s leading movement-and-rewards platform, scaling globally while using technology, data, and smart incentives to drive lasting behavior change and wellbeing at scale.

About the role

Reporting to the Growth team, alongside Charles, you'll work as a Backend Engineer focused on delivering value for our Growth squad: shipping features, managing the run, and helping the team move fast without breaking things.

At WeWard, we're entering an exciting new phase of evolution — expanding far beyond a simple step counter. You'll have the opportunity to work on major upcoming growth initiatives!

You’ll face the challenge of operating a large-scale international platform handling billions of interactions and strong peaks of activity every day. Excellence is key: in a consumer app used worldwide, every percentage point of performance, stability, or quality directly translates into user growth, or loss.

The Growth Squad at WeWard works on 3 core elements: Acquisition, Engagement & Retention.

Acquisition means finding key events users do that indicate they are power users, and optimize advertising algorithm platforms to target similar users for us to have the best leads.

Engagement is about creating meaningful touch-points with our users, motivating them to open the app daily and build lasting habits. A core part of this is empowering business owners with a robust campaign platform to reach the right users with the right message, through the right channel.

Retention is about keeping users hooked and winning back those who've drifted away. We run continuous A/B tests across all our actions and channels to uncover the levers that drive users back into the app — and double down on what works.

Your impact/responsibilities

As a Senior Backend Engineer inside the Growth Squad, you will:

Ship and own

• Design, develop, test, and deploy reliable, maintainable code: APIs, scripts, backend processing, with a strong sense of ownership over what you build

• Lead the evolution of Echo, our internal communication platform, with the ambition to handle any campaign type at scale

• Craft new communication channels to interact with users, whether in-app (events, in-app messaging) or outside (Live Activities, widgets)

• Take initiative and lead projects end-to-end, from scoping to production

Drive technical excellence

• Optimise critical code path; identify bottlenecks and implement concrete solutions

• Contribute to architecture decisions at the pillar level, and ensure their consistency over time in coordination with the CTO and Engineering Manager

• Identify and elevate technical risks before they become incidents: fragile areas, critical debt, security concerns

• Drive long-term technical debt reduction without derailing the roadmap

Collaborate and mentor

• Work upstream with PMs to assess feasibility, frame trade-offs, and build realistic delivery plans

• Provide day-to-day guidance to pillar engineers on complex technical decisions and knowledge sharing

Our stack is mainly Python (Flask, FastAPI), but we value more the ability to design scalable architecture than the language you use.

You should be comfortable working on infrastructure at scale, where optimization and performance is the key to handle our millions of users.

You should care as much as possible about code quality while remaining pragmatic about delivering value to users. It’s important to have a clear vision of the ideal architecture we should aim at.

Beyond pure development, we expect you to understand what is at stake for the business, and help stakeholders to give birth to their vision

Our commitments

• SUCCEED — You’ll join a team of passionate people who share values of ambition and determination

• TRUST — We give you real autonomy, trusting you to reach your goals in your own way

• EXPLORE — You’ll grow in a culture that’s constantly evolving and curious about what’s next

• PROGRESS — We’ll support you through challenges, learn from mistakes, and move forward together

• SMILE — And every day, you’ll be part of a fun and positive environment where humor is always welcome

Preferred experience

What we’re looking for

You’re the perfect match if…

• You have 6+ years of experience as a Backend Engineer, with hands‑on exposure to large‑scale, high‑traffic systems and a strong sense of ownership over what you build.

• You love combining continuous improvement and agility, always bringing new ideas to the table. At WeWard, our spirit is Test & Learn — we deploy to production more than ten times a week!

• You have a natural interest in the startup world and want to make a tangible impact in your next adventure.

• You’re motivated by contributing to the health and wellness sector.

• You’re eager to evolve in an international environment — WeWard is now present in Spain, Italy, the US, Germany, the UK, and more!

What we offer

• A global, mission-driven team with teammates in Paris, NY, London, Boston!

• A healthy work/life balance (we walk the talk)

• Annual learning & dev budget (you grow, we grow)

• Hybrid work, with 2 days of remote work per week

• (Really, really) Cool office in central Paris with snacks, a walking desk and a huge Wardy hanging around

Recruitment Timeline

1. 30-min technical chat with Charles, your future manager, to dive into the role and missions.

2. A case study followed by a 1 hour debrief with Charles and Surya, including time for mutual feedback.

3. 30-min HR talk with Kaënaath, our TA  Specialist

4. Office tour to meet other team members.