Senior AI Engineer Tech Paris

Weflayr SAS; Paris; On-site; EUR 90,000 - 130,000; Full time

Benefits offered by this job

Equity

Job summary

Weflayr SAS in Paris is seeking an experienced AI/Backend engineer to own and improve the AI stack, routing and benchmarking tooling, and production AI agents. You will work closely with the CTO and the tech team to implement scalable solutions.

The role emphasizes hands-on coding, research-driven development, CI/CD, and deploying to cloud, with a pragmatic focus on delivering real user value. Flexible on-site with occasional remote days as the early-stage team grows.

Qualifications

• 5+ years of professional experience in AI/Backend including: 2 years on a traditional ML / DL project; 1 year building AI agents in production.

Responsibilities

• Improve benchmarking & evaluation tooling.
• Improve prompt caching tooling to optimise it for our clients
• Improve model routing algorithm
• Build new AI tooling / algorithms for the future
• Continuously keep up with latest research and trends and propose ideas
• Contribute to the codebase to deploy your work

Skills

AI/Backend

CI/CD

API development

Production ML/DL

AI agents in production

Tools

vLLM

DVC

GitHub Actions

Job description

Weflayr is an AI gateway built to give its users the highest level of control and quality on dynamic model routing. It routes using each user’s own past data: each candidate model is benchmarked on it, and the routing engine uses the results to pick the best model for each call.

We raised a $2.5M pre-seed and are incubated in the F/AI program. We have opened the product to a small group of beta testers and plan to release it globally in the coming weeks.

About the role

You will own the development and improvement of Weflayr’s AI stack, which is our core competitive edge. Example tasks that you will be doing:

• Improve our benchmarking & evaluation tooling
• Improve our prompt caching tooling to optimise it for our clients
• Improve our model routing algorithm
• Build the new set of AI tooling / algorithms that will shape the future of Weflayr (we can’t say much here but happy to discuss it)
• Continuously keep up with the latest research and trends that could be interesting for us, assessing them when relevant, and proposing new ideas.
• Contribute to the codebase to deploy your work

We are a very horizontal team: you will work hand in hand with our CTO, Noé Achache, and the rest of the tech team.

Based in Paris: we truly believe that to achieve great things, we need to be together, to celebrate the good times, support each other through the harder ones, and above all because, at such an early stage, the most important decisions are made in informal discussions. We do offer some flexibility to suit everyone’s needs, e.g., working remotely one day a week, or a full week a couple of times a year.

What we are looking for

You are a good fit for this job if:

• You are looking for a big challenge, and want to take on a high level of ownership, with the level of proactivity and dedication that is needed to succeed. You want to take pride in contributing to the success of Weflayr as a whole, rather than succeeding on your own individual subjects.
• You have 5+ years of professional experience in AI/Backend including:
  • 2 years on a traditional ML / DL project
  • 1 year building AI agents in production: we want you to have the relevant experience to understand the pain of our clients
• You have very strong skills in both research AND development:
  • Research:
    • It is common practice for you to generate an idea / build intuition, lead the experiment, validate your ideas and render the results in a way that can be easily understood, even by a newcomer arriving 6 months later in the company
    • You are obsessed with validating your experiments by looking at specific examples rather than simply watching generic metrics
  • Development:
    • It is common for you to set up a CI, deploy your work to the cloud, build an API (even without AI)
    • You have already worked with large codebases in production with several contributors
• You write 100% of your code with AI, but still use your engineering skills to plan/validate your work
• You have very good soft skills (communication, adaptability, collaboration, …)
• Although you are a technician, you also care deeply about the product, and you take pride in seeing your work being used by real users.
• Being pragmatic is your core value: what drives you is to build things that work when needed rather than building something super advanced that may not be needed.

Technical stack

• Others: vLLM, DVC, GitHub Actions

Our team

We are a small team (currently 3 people + freelancers) working hand in hand.

Our founders:

• Romain Mazeries, co-founder & ceo: Former co-founder and CEO of MangoPay, a payment fintech company he built and scaled up to 120M€ in annual revenue.
• Noé Achache, co-founder & cto: Former Head of AI Engineering at Theodo Data & AI, where he led the development of various ML/DL projects and AI agents in production.

Compensation

We offer a competitive salary + equity based on seniority.

Process

• 45 min on coding and engineering skills with Noé (CTO) (video call)
• 45 min on AI skills with Noé (CTO)
• 30 min with Romain (CEO)
• Coffee or lunch with the founders, to make sure there is a mutual fit

Benchmark your real calls, approve the models you trust, and put them to work with a routing strategy built around your business.