Scalable backend systems,engineered for 0 → 100x.
I'm Anup Kumar — Architect / Principal Engineer with 13+ years designing APIs, distributed systems, and infrastructure that served 200M+ users at Bolt (Berlin) and Delivery Hero. Now helping founders and teams scale without breaking.
Backend, architecture, and the hard parts.
I focus on the systems most teams don't have the time — or the scars — to build properly.
Case studies, not a GitHub dump.
Scaling the Bolt+ Campaigns Platform
Led end-to-end architecture and scaling of Bolt+ campaign infra — drove 15% user-base growth and 5% food-delivery revenue lift across 200M+ MAU.
Inventory Management with a State Machine
Modelled warehouse stock movement as a finite state machine — safer transitions, zero ghost-stock bugs.
I think in diagrams. Here are two.
Field notes from production.
Designing Idempotent Payment APIs
How to prevent duplicate charges in distributed systems — the contract, the storage, and the failure modes I learned at scale.
Building a Distributed Rate Limiter with Redis
Sliding window vs fixed window, why I chose sorted sets, and how the rate limiter at Bolt protected a 10K-RPS platform.
Circuit Breakers, Done Right
Most circuit breakers protect nothing. Here's how to place them, tune them, and avoid the worst failure mode — circuit-breaker-induced outages.
Have a system that needs to scale — or stop breaking?
I work with a small number of teams each month on architecture reviews, scaling, and hands-on backend engineering. If that sounds like you, let's talk.