From Interview Task to Production Protocol

In summer 2020, a University of Washington PhD student joined Cloudflare's research team as a fully remote intern. The project she ended up contributing to—Oblivious DNS over HTTPS (ODoH)—wasn't even on her radar when the pandemic began. By the end of the internship, that work would be published at PETS 2021 and win the Andreas Pfitzmann best student paper award.

Getting in the Door

The process started with a LinkedIn application, followed months later by a call from a recruiter who confirmed the internship would be remote. The interview loop involved a take-home programming task, a pair programming session, and conversations with research leads.

The programming task came from Nick Sullivan with a concrete goal: add certificate transparency report support to CFSSL, Cloudflare's open source PKI toolkit. Specifically, the work required extending cfssl-scan—a tool that already checked hostnames for connectivity, TLS information, TLS session support, and certificate data—with a new scanner family that queried Certificate Transparency logs and folded that data into the output. After several rounds of design feedback by email, the submission included a draft explaining the design rationale, supported features, and error handling behavior.

The pair programming interview with Watson Ladd covered research interests, active Cloudflare projects, and then a live coding exercise that emphasized design reasoning, extensibility, code reuse, and test coverage. The remaining interviews focused on the candidate's academic work and where it might align with Cloudflare's research priorities. An offer followed.

Choosing ODoH

Onboarding was smooth—documentation was clear, access control worked immediately, and all internal resources were available from day one. The bigger challenge was focus: with so many open research problems, narrowing down to one project for the summer took deliberation. After a week of conversations with researchers and literature review, the choice was ODoH.

The protocol, proposed at the IETF, targets a specific privacy gap in DNS. When clients use DNS over HTTPS (DoH) to query Cloudflare's recursive resolver, the encrypted channel protects query content and responses, but the client IP address is still visible to the resolver. Oblivious DNS over HTTPS separates those concerns using a proxy architecture so the resolver never sees the client's IP and the proxy never sees the query content.

Working with advisors and engineers, the intern built interoperable ODoH implementations in Go and Rust, deployed them experimentally on cloud services, and ran measurements of the protocol. That work surfaced security and performance issues, drove iterative design improvements, and eventually moved into production with help from Cloudflare's engineering and reliability engineering teams. The open source implementations doubled as reference material for IETF and OARC presentations. The resulting paper was accepted at PETS 2021 and received the best student paper award.

Beyond the Code

The remote internship wasn't solely technical work. Cloudflare's research team operates like an academic lab, with scheduled paper reading groups. A random engineer chat program matched the intern with people across the company, and weekly intern hangouts built social connections. Time zone differences made those hangouts harder to catch consistently, but the access to design, legal, content, and engineering teams throughout the organization was a highlight.

Presenting the ODoH work live on Cloudflare TV was the most nerve-wracking part—support from the TV team and research colleagues made it manageable.

Key Takeaways

Cloudflare's model of moving research from prototype to production depends on transparent collaboration across internal teams and with academia. The shared mission of building a better Internet lets contributors from different disciplines plug into the same problem. The intern's own assessment is candid: she got lucky finding a problem that was personally interesting and aligned with Cloudflare's goals—and the result depended on hundreds of people across media, design, legal, engineering, and research teams, not just the handful directly involved in ODoH.

Cloudflare Research is accepting applications for 2022 internships.