Senior

Scale Reddit's Core API Platform behind hundreds of millions of users

Interview for a Senior Software Engineer role on Reddit's Core Platform team, the group that runs the APIs powering listings, posts, comments, and media for Reddit. Expect deep questions on distributed systems design, media delivery pipelines, and mentoring junior engineers while keeping a mission-critical API at 5+ nines of availability.

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What this interview tests

Large-scale distributed systems design (Golang/Python)
API platform architecture at high QPS with 5+ nines availability
Media delivery performance and scalability across the stack
Mentoring and technical coaching of junior engineers
Operating and scaling services owned by a fast-growing org

Common question themes

Design a system that serves hundreds of thousands of TPS reliably

Debugging a production incident in a distributed API platform

Optimizing media delivery from backend to end user

Mentoring a junior engineer through a technical disagreement

Trade-offs between shipping velocity and system reliability

How candidates describe it

Real Senior Software Engineer interview stories — retold from candidates' public write-ups, with sources.

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