Senior Fullstack TypeScript Developer (Product Engineer)

lemlist

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Location: Nantes
Job Type: full-time
Work Format: 🌍 Remote EMEA
Salary: Salary between 60K€ and 70K€ fixed salary + 18K€ bonus
Posted: August 11, 2026

Job Description

🚀 About lemlist

lemlist is a global B2B SaaS business with the mission to help any business grow.

We are doing over $54M in ARR while being:

Bootstrapped
Profitable
A small, agile team of 170 highly talented people, remote-friendly
Majority owned by an entrepreneur, Guillaume Moubeche, Founder & Chairman — which gives us maximum freedom

We operate 2 business lines:

Sales Engagement with our flagship products lemlist & Claap, generating $49.5M ARR and growing over 50% year over year
Personal Branding with Taplio & Tweet Hunter, generating $4.5M ARR

lemlist is a highly ambitious company that aims to become a world-class giant in the Sales Tech space.

Our mantra: Keep growing – and we live by it every day.

Job Description

We're looking for a Senior Fullstack TypeScript Developer to join our team. You'll be responsible for designing and developing new features for our SaaS products. We need someone who is passionate, autonomous, and loves technical challenges.

Your main missions will be:

Design and develop new features from scratch, both on the frontend and backend, Independently developing new features that enhance user experience and increase product functionality.
Stepping into the role of technical lead within your squad, driving excellence and setting standards.
Improve the code base with refactoring, bug fixes, and optimization
Work on multiple projects simultaneously
Help the customer support team on technical issues, providing prompt and effective solutions
Facilitating knowledge sharing and capacity building by training fellow developers, enhancing overall team competency and productivity.

Key results

Within 3 months you will have

Successfully onboarded and integrated into the team
Developed a deep understanding of our B2B SaaS products and their technical requirements
Contributed to the development of new features and improvements to our existing code base

Within 12 months you will have

Played a key role in the development and delivery of multiple successful projects
Made significant contributions to the optimization and scalability of our software products

What’s in it for you?

Work in a profitable, bootstrapped, and high-growth company that doesn’t rely on external funding to live.
You will have the opportunity to make a lasting impact on a suite of products that are changing the game in multiple industries.
Work with passionate senior engineers who share their knowledge and expertise
Great ownership of your work. You will be part of a dynamic, innovative, and passionate team that respects autonomy and encourages individual input.
No endless meetings
Full remote policy
You will grow professionally and personally, enhancing your technical skills and expanding your global network.

Preferred Experience

Must have

You’re an expert in TypeScript / JavaScript with at least 7 years of XP
You have a proven track record in building and maintaining web applications.
You have a robust understanding of NodeJS and MongoDB, and ideally React
You’re able to work independently and take ownership of complex projects
You’re a fast learner
You’re comfortable with the agile methodologies
You like to communicate
You like to work remotely, Gather, Slack and Notion are your best friends
You are adaptable and like to discover new things and you can work on front-end integration, back-end development, mongo optimization, performance issues and more
You speak French and English and you are in the French timezone

Nice to have

You have a first experience in B2B SaaS startup
You are self-taught, you have been developing personal projects since you were a child or in the evenings and weekends. This is not mandatory but a big plus for us, we are all passionate about programming and like to create things, both at work and outside

Additional Information

Salary between 60K€ and 70K€ fixed salary + 18K€ bonus
Where you live, and work is totally up to you – we do have an office in Paris if you enjoy life at the office 🇫🇷
Profit sharing: When lemlist wins, all team members share the profits
Alan Blue: Comprehensive 100% premium medical coverage for you and your family
Swile Meal Tickets: Enjoy daily meal tickets to fuel productivity
Navigo Card: Seamless commuting with a 100% covered Navigo card
Full-remote Work Setup: A well-funded home office budget to ensure seamless remote work
Gear: Get a 48GB Macbook Pro + tools and equipment you need for your job
Team building: We all meet once per year at really cool places around the world (you can check our video here ;)

Recruitment process

Interview with Lucas our TAM
Technical interview with Corentin, our VP of Engineering
Technical Interview with Mickael, our CTO
Interview with Charles, our CEO

🎯 Who is this job for?

Senior-level role for an autonomous Product Engineer with 7+ years of TypeScript/JavaScript experience and strong expertise in Node.js, MongoDB, web applications, and ideally React.

The ideal candidate can design and deliver fullstack SaaS features independently, lead technical initiatives, optimize performance and scalability, refactor code, resolve technical support issues, and manage multiple projects in an agile remote environment.

They should be comfortable mentoring developers, communicating clearly, learning quickly, taking ownership of complex work, and speaking both French and English while working in the French time zone.

💬 Potential Interview Questions

How would you design a new end-to-end feature in a TypeScript SaaS application?

I would start by clarifying the user problem and defining the API, data model, frontend states, and acceptance criteria. I would then implement the backend and frontend incrementally, add tests and observability, and validate the feature with product and support stakeholders.

How would you structure a Node.js and TypeScript backend for maintainability and scalability?

I would separate transport, business logic, data access, and shared domain types into clear modules. I would enforce strict TypeScript settings, consistent error handling, input validation, automated tests, and dependency boundaries to keep the codebase evolvable.

How would you optimize a slow MongoDB query in a production application?

I would inspect the query with explain plans, measure execution time and document examination, and verify that filters and sort operations use appropriate indexes. I would also review schema design, projection, pagination strategy, and query frequency before changing the implementation.

How would you design MongoDB indexes for a multi-tenant B2B SaaS product?

I would include the tenant identifier in indexes where queries are tenant-scoped, followed by the most selective or frequently filtered fields. I would validate index usage with realistic workloads and balance read performance against write overhead and storage costs.

What practices do you use to ensure type safety across a React frontend and Node.js backend?

I would share domain types or generate types from a single API contract, while validating all external input at runtime because TypeScript types do not protect against untrusted data. I would also use typed API clients, strict compiler settings, and contract tests to detect breaking changes.

How would you investigate and resolve a performance issue affecting a SaaS web application?

I would first reproduce the issue and establish measurable metrics, then use frontend profiling, backend logs, database query analysis, and distributed tracing to locate the bottleneck. After applying a targeted fix, I would load-test the relevant path and monitor the result in production.

How would you handle asynchronous jobs and retries in a Node.js application?

I would make jobs idempotent, persist their state, and use bounded retries with exponential backoff for transient failures. Permanent failures should be recorded for investigation, while timeouts, dead-letter handling, and metrics should prevent a failing dependency from blocking the system.

How would you lead the technical delivery of a complex feature within an agile squad?

I would clarify scope and risks, break the work into independently deliverable increments, and document key technical decisions. I would keep communication transparent, review designs and code, remove blockers, and ensure quality through testing and incremental releases.

How would you safely refactor a critical TypeScript codebase while continuing feature development?

I would first establish characterization tests and identify a small, well-defined boundary for the refactor. I would make incremental changes behind stable interfaces, review each step, and use metrics or feature flags when behavior or performance could change.

How would you diagnose and resolve a technical issue reported by customer support?

I would gather the customer context, affected tenant, timestamps, reproduction steps, and relevant logs before assessing severity and impact. I would provide a clear workaround or fix, communicate progress to support, and document the root cause and preventive action.

📋 Job Summary

lemlist is a profitable, bootstrapped global B2B SaaS company helping businesses grow through its sales engagement and personal branding products. As a Senior Fullstack TypeScript Developer, you’ll build features from scratch, lead technical initiatives, improve performance and code quality, support customers, and mentor fellow developers. Work fully remotely from the French timezone with a stack centered on TypeScript, JavaScript, Node.js, MongoDB, and ideally React, for €60,000–€70,000 fixed salary plus an €18,000 bonus. Apply to enjoy high autonomy, meaningful product impact, profit sharing, excellent benefits, a home-office budget, premium equipment, and a talented remote-first team.