Nebius

Runs GPU clouds for AI training and deployment

Senior Software Engineer - Agentic Search, Web Access Engineer

Backend EngineeringConfirmed live in the last 24 hours

Full-timeZürich, SwitzerlandNo salary listedIn-person

About the Job

Requirements

At least 5 years of experience building production systems.
Expertise in several areas of the request lifecycle, client-side analysis, or production operation described in the posting.
Knowledge of HTTP/1.1, HTTP/2 and HTTP/3, TLS handshakes and TLS fingerprints (JA3/JA4), and header behavior.
Understanding of what a server can observe and what a client controls at each step of a request.
Ability to debug by replaying captured browser traffic, comparing it with a real browser on the same network path, and changing one variable at a time.
Ability to read and analyze complex or obfuscated JavaScript and observe script measurements by hooking browser APIs.
Understanding of how browser, device, and network characteristics are measured, including canvas, fonts, WebGL, screen metrics, and window metrics, and how these characteristics remain consistent across layers.
Experience using browser instrumentation and the Chrome DevTools Protocol for investigation.
Production experience with measurable results, including requests per day, sites or hosts, success rate, and how success was measured.
Strong programming ability in at least one of Go, Python, Rust, or C++.
Authorization to work in the country in which the applicant applies, with proof of employment eligibility required as a condition of hire.

Responsibilities

Diagnose failed or degraded requests at the appropriate layer, including network and IP, TLS and HTTP/2 behavior, headers and session state, client-side scripts, or browser characteristics.
Analyze how websites verify and classify clients, including how client-side scripts and protocol-level behavior affect what a site serves to different clients.
Build clients and tooling that behave consistently and compatibly with standard browsers across these layers, using a real browser when a lightweight client is insufficient.
Monitor access quality as websites change, detect regressions, identify their causes, and measure success using real content rather than status codes.
Build tooling for traffic capture and comparison against real browsers, per-site and per-method success tracking, and measurement of the cost of each successful fetch.
Choose a fetch method for each host, from a lightweight HTTP client to a full browser, balancing quality against cost.
Investigate and fix causes when a site returns a different response to the company's client than to Chrome on the same network path.
Identify and adapt to changes in how sites verify clients, and make future changes easier to detect.
Investigate why browser-like network profiles produce worse results on some hosts and determine what no longer matches.
Participate in coding interviews as part of the hiring process.

Desired Qualifications

Experience working at a web data provider, browser or web-security company, or a company that collects data from complex sources.
Contributions to browser networking or fingerprinting-related open-source tooling, or public write-ups explaining how client verification works.
Experience building or maintaining a patched browser.
Experience with networks, proxies, and IP reputation.
Experience with internet-scale distributed systems, Kubernetes, and cloud infrastructure.

About Nebius:

Nebius is leading a new era in cloud infrastructure for the global AI economy. We are building a full-stack AI cloud platform that supports developers and enterprises from data and model training through to production deployment, without the cost and complexity of building large in-house AI/ML infrastructure.

Built by engineers, for engineers. From large-scale GPU orchestration to inference optimization, we own the hard problems across compute, storage, networking and applied AI.

Listed on Nasdaq (NBIS) and headquartered in Amsterdam, we have a global footprint with R&D hubs across Europe, the UK, North America and Israel. Our team of 1,500+ includes hundreds of engineers with deep expertise across hardware, software and AI R&D.

The Product

In a rapidly evolving world, trust in AI depends on AI agents being grounded in fresh, verified real-world data. Search is the foundation that makes this possible.

We are building an agent-native search platform designed specifically for AI systems rather than human users. Our product provides programmatic, low-latency, and observable search APIs that AI agents use to retrieve, filter, and reason over real-world information at scale.

The Role

We are looking for a Senior Software Engineer to work on the web access infrastructure of a novel search engine tailored for agentic AI consumption.

In this role, you will focus on making our access to public web content reliable and efficient. You will investigate how modern websites and browsers communicate across the full request lifecycle, find the root cause when a request fails or returns something unexpected, and build the fixes into production systems operating at internet scale. Your work ensures that high-quality content is consistently available to the crawling, indexing and retrieval systems downstream.

In this position, your responsibility will be to

Diagnose failed or degraded requests at the right layer: network and IP, TLS and HTTP/2 behavior, headers and session state, client-side scripts, or browser characteristics
Analyze how websites verify and classify clients, including how client-side scripts and protocol-level behavior shape what a site serves to different clients
Build clients and tooling that behave consistently and compatibly with standard browsers across all of these layers, using a real browser where a lightweight client is not enough
Monitor access quality as websites change: detect regressions, find the cause, and measure success on real content rather than on status codes
Build the tooling to do this at scale: traffic capture and comparison against real browsers, per-site and per-method success tracking, and the cost of each successful fetch
Choose the fetch method for each host, from a lightweight HTTP client to a full browser, balancing quality against cost

You may be a good fit if you

Have 5+ years of experience building production systems, and are an expert in several of the following areas.

The request lifecycle

HTTP/1.1, HTTP/2 and HTTP/3, TLS handshakes and TLS fingerprints (JA3/JA4), and header behavior
What a server can observe at each step of a request, and what a client controls at each step
A debugging method, not guesses: replaying captured browser traffic, comparing against a real browser on the same network path, and changing one variable at a time

Client-side analysis

Reading and analyzing complex or obfuscated JavaScript, and observing what a script measures by hooking browser APIs
How browser, device and network characteristics are measured (canvas, fonts, WebGL, screen and window metrics) and how consistent they are across layers
Browser instrumentation and the Chrome DevTools Protocol, used as tools for investigation

Running it for real

Have run this in production and can give numbers: requests per day, sites or hosts, and the success rate and how you measured it
Strong programming in at least one of Go, Python, Rust or C++

Strong candidates may also have experience with

Working at a web data provider, a browser or web-security company, or a company that collects data from complex sources
Contributions to browser networking or fingerprinting-related open-source tooling, or public write-ups of how client verification works
Building or maintaining a patched browser
Networks, proxies and IP reputation
Internet-scale distributed systems, Kubernetes and cloud infrastructure

The kind of problems you will work on

A site returns a different response to our client than to Chrome on the same network path. Find out why, and fix that cause.
A site changes how it verifies clients and success drops across a group of sites. Find what changed, adapt, and make the next change cheaper to catch.
Switching to a browser-like network profile makes results worse on some hosts. Work out what no longer matches.

We conduct coding interviews as part of the process.

Benefits & Perks:

Competitive compensation
Career growth and learning opportunities
Flexibility and ownership
Collaborative and innovative culture
Opportunity to work on impactful AI projects
International environment and talented teams

What's it like to work at Nebius:

Fast moving - Bold thinking - Constant growth - Meaningful impact - Trust and real ownership - Opportunity to shape the future of AI

Equal Opportunity Statement:

Nebius is an equal opportunity employer. We are committed to fostering an inclusive and diverse workplace and to providing equal employment opportunities in all aspects of employment. We do not discriminate on the basis of race, color, religion, sex (including pregnancy), national origin, ancestry, age, disability, genetic information, marital status, veteran status, sexual orientation, gender identity or expression, or any other characteristic protected by applicable law.

Applicants must be authorized to work in the country in which they apply and will be required to provide proof of employment eligibility as a condition of hire.

If you need accommodations during the application process, please let us know.

About the Company

Nebius

Runs GPU clouds for AI training and deployment

Nebius runs an AI cloud for developers, researchers, and enterprises that train models and put them into production. Its AI Cloud combines GPU computing, storage, networking, and managed services, while Token Factory runs models through an API so teams do not manage the underlying servers. Customers rent computing and storage at usage rates or reserve capacity, choosing resources that fit short experiments or sustained production workloads. Beyond the cloud, the group owns Avride, which develops autonomous vehicles and delivery robots, and TripleTen, which teaches technical skills for people changing careers. The publicly listed group is headquartered in Amsterdam, Netherlands.

Company size: 1,001-5,000
Company stage: IPO
Headquarters: Amsterdam, Netherlands
Founded: 1997

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