Postgres Internals I
This document discusses a few high-level concepts of PostgreSQL’s internals. Even though these are not needed in day-to-day activities, knowing them would certainly help understand queries and ...
Gems of Coding
System Design - Rate Limiter
Rate limiter is a vital component in large-scale web applications, as it controls traffic to the application servers to ensure a smooth experience for the majority of the users. It has become a cri...
DDIA - Chap01 - Reliable, Scalable and Maintainable Applications
A majority portion of web applications are largely data-intensive, and not compute-intensive. The speed of fetching the overall data to process the requests is generally the limiting factor as is a...
RAFT Consensus Algorithm
One of the foundation problems of designing a distributed system is how to store some data in a distributed system. One basic approach is to share or duplicate all the data between the nodes. Howev...
PostgreSQL - Making Double Bookings Impossible
Every hotel reservation system starts with the same line of code: SELECT 1 FROM reservation WHERE room_id = $1 AND check_out > $2 AND check_in < $3; -- no rows? great, book it And every on...
Inference Engineering - Part 1: How a Model Gets Made
I kept running into large language model (LLM) systems and finding that I could use them without understanding them. That is an uncomfortable place to be: you end up accountable for behaviour you c...
Production RAG - Part 9: Splitting an Answer into Claims
Part 7 argued that a groundedness gate has to score atomic claims and take the minimum, because a five-sentence answer with one fabrication averages out to a passing score. It then moved on, having...
Production RAG - Part 8: Evaluation and Operations
Seven posts of machinery, and none of it is trustworthy until you can answer one question: how do you know it works? RAG systems are unusually hostile to intuition here, because a broken one keeps ...
Production RAG - Part 7: Grounded Generation
Retrieval can succeed completely and the answer can still be wrong. The model receives five relevant chunks and asserts a sixth thing that none of them support — a plausible number, a policy that d...
Production RAG - Part 6: Entities and Knowledge Graphs
At some point in every RAG project, a category of question stops working and no amount of tuning fixes it. Better chunking does not help. A stronger reranker does not help. The reason is that two c...