Senior Software Engineer - High Performance Computing (HPC)

The Trade Desk is a global technology company and the world’s leading independent platform for digital advertising, with nearly 4,000 employees across more than 30 offices. Our technology helps advertisers reach the right audiences across the open internet — from streaming TV and podcasts to mobile apps, news, and more. Advertising powers the content people love. By making it more transparent, effective, and responsible, we help support trusted journalism, quality entertainment, and creators worldwide. The world’s brands and agencies rely on us to reach their customers and grow their businesses responsibly. The scale of our platform brings unique technical challenges — from processing massive datasets in real time to building systems that operate reliably on a global scale. When you work here, your impact is worldwide. We welcome diverse perspectives, encourage curiosity, and build teams that learn from one another. If you’re driven to solve meaningful challenges, we’d love to meet you. What we do: Our Software Engineers are end-to-end owners: you design, build, and operate the systems that power our platform. We are part of the High Performance Computing (HPC) team, which supplies the core bidding platform with data and guarantees its availability, freshness, and quality. Within HPC, the First Party taskforce owns how advertisers bring their own data onto our platform, and how that data is priced and monetized. Three connected domains: Bringing an advertiser's own customer data onto the platform. Advertisers arrive with their own customer lists. We ingest that data, anonymize it so the underlying personal information is never exposed, and make it usable for advertising. Capturing what people do on an advertiser's own site. Tracking pixels that fire when someone views a product or completes a purchase. One signal, two jobs: it proves which ads drove the sale, and it lets the advertiser re-reach the visitors who didn't buy. Pricing and charging for platform usage. Working out what each customer owes and why. This feeds billing directly, so a wrong number is a real problem, not a rounding error. Concretely: GraphQL APIs behind customer-facing workflows, Kafka-driven asynchronous pipelines moving data between services and regions, and the transactional stores that keep it all consistent — running 24/7 across multiple regions. You will work across two stacks, C#/.NET and Kotlin on the JVM, with real-time ingestion, services, and APIs spread across both — so comfort moving between languages matters more than depth in either one. What you'll do: Own systems end to end — design, production, and on-call. Build and maintain backend services and GraphQL APIs used by internal teams, customers, and partner integrations. Build the pipelines that ingest, validate, and anonymize first party data, turning advertiser PII into tokens that can be targeted on the platform. Work inside a secure enclave where PII must never touch general-purpose infrastructure, and design around that constraint rather than against it. Get asynchronous correctness right — retries, ordering, idempotency, partial failure — where a message can arrive twice, late, or out of order. Own cross-system changes across services, APIs, and databases, with the test coverage, observability, and monitoring to prove they hold. Turn ambiguous requirements from product and business partners into designs, and shape long-term technical strategy. Raise the bar around you through code review, design feedback, and mentoring. We are a global team with different backgrounds, experiences, and perspectives. To complement this team, you will welcome ideas that are different from your own, and work to build from common ground—valuing and fostering both visible and invisible dimensions of diversity. Who you are: Extensive experience building and operating production systems in high-scale or high-impact environments. Solid CS fundamentals and hands-on breadth across distributed systems: .NET/C#,…