Sushant Kumar Gupta | Searcharxiv

arXiv2026

The Computer System Trail

No matter how much the world of computing changes, system design remains crucial. While most people try to learn it through quick tutorials or AI-generated summaries, there is no better way to master the field than by studying the original research papers. This book serves as a roadmap through those foundational texts, covering seminal papers in distributed systems, operating systems, and big data. It doesn't just look at what these systems do; it digs deep into why they were built that way. Built from years of notes taken during discussions at top universities and industry meetups, this guide helps readers understand how systems work under the hood. It is for those who are tired of surface-level content and want to develop the technical patience to wrestle with complex problem-solving. Readers will find the journey long and challenging but highly rewarding, as it enables them to elevate their engineering craft to a truly professional level.

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arXiv2025

Formal Specification for Fast ACS: Low-Latency File-Based Ordered Message Delivery at Scale

Low-latency message delivery is crucial for real-time systems. Data originating from a producer must be delivered to consumers, potentially distributed in clusters across metropolitan and continental boundaries. With the growing scale of computing, there can be several thousand consumers of the data. Such systems require a robust messaging system capable of transmitting messages containing data across clusters and efficiently delivering them to consumers. The system must offer guarantees like ordering and at-least-once delivery while avoiding overload on consumers, allowing them to consume messages at their own pace. This paper presents the design of Fast ACS (an abbreviation for Ads Copy Service), a file-based ordered message delivery system that leverages a combination of two-sided (inter-cluster) and one-sided (intra-cluster) communication primitives - namely, Remote Procedure Call and Remote Memory Access, respectively - to deliver messages. The system has been successfully deployed to dozens of production clusters and scales to accommodate several thousand consumers within each cluster, which amounts to Tbps-scale intra-cluster consumer traffic at peak. Notably, Fast ACS delivers messages to consumers across the globe within a few seconds or even sub-seconds (p99) based on the message volume and consumer scale, at a low resource cost.

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