Senior Rust Engineer Own the Rust stack that runs our gateway in production. Tech Paris

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

Benefits offered by this job

Equity

Flexible working schedule

Job summary

Weflayr SAS in Paris is seeking a Backend Engineer to own our Rust stack that runs the gateway in production. You will add capabilities like speech-to-speech, support new providers, and improve latency.

You will work closely with the CTO Noé Achache and a small tech team, with flexibility for remote work one day a week or longer blocks a few times a year.

Qualifications

• 5+ years of professional Backend experience including 2-3+ years in Rust.
• Familiarity with telemetry tools like OpenTelemetry or Sentry and error-tracking methodologies.
• Experience operating a backend in production with attention to retro-compatibility.
• Infra experience: replication of databases across regions and edge deployment.
• Ability to work across Rust and Python stacks and collaborate with the CTO.

Responsibilities

• Own and extend the Rust stack powering the production gateway.
• Add capabilities to the gateway (e.g., speech-to-speech, new providers).
• Maintain production gateway with latency tracing and PR work.
• Contribute to the Python stack for screening pipelines and related tooling.

Skills

Rust

Backend development

Telemetry tools

OpenTelemetry

Sentry

Tools

OpenTelemetry

Sentry

GitHub Actions

PostgreSQL

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 be the owner of our Rust stack which runs our gateway in production. Example tasks that you will be doing:

• Add new capabilities to the gateway such as speech-to-speech, supporting new providers, etc.
• Maintain the gateway in production: fix errors, track latency, build AI agents to track production and make PRs, etc.
• Improve the latency of the gateway, through application-level optimisations in Rust as well as infrastructure optimisations
• Contribute to the Python stack e.g. to improve our LLM screening pipeline

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 Backend including 2-3+ years of Rust
• You already operated a backend in production. You are familiar with standard telemetry tools like OpenTelemetry or Sentry, error tracking & fixing methodology, attention to retro-compatibility, …
• You are comfortable with infra: e.g. replicating a Postgres database across regions for latency, deploying to the edge, owning what you ship to production
• You are more of a Swiss Army knife than a purist: if something outside Rust is blocking the team, you jump on it
• 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 Rust skills (video call)
• 45 min engineering 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.