Sachin Tolay

@tolaysachin

BurnabyJoined June 2025

About

I am here to share everything I know about computer systems: from the internals of CPUs, memory, and storage engines to distributed systems, OS design, blockchain, AI etc. Deep dives, hands-on experiments, and clarity-first explanations.

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Sachin Tolay's blogs

Breaking Down Systemsnihcas.hashnode.dev15 posts

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nihcas.hashnode.dev

From Sessions to JWTs: How Distributed Systems Reshaped Identity

The evolution of identity mechanisms closely followed the evolution of distributed systems. This article walks through that progression and the problems each step tried to solve. Before Identity (Early–Mid 1990s) In early web applications, identity w...

Dec 15, 20256 min read

nihcas.hashnode.dev

Memory Models Explained: How Threads Really See Memory

Modern processors and compilers aggressively reorder instructions to improve performance → a behavior we explored in detail in my previous article: Instruction Reordering: Your Code Doesn’t Always Run in the Order You Wrote It. To write correct concu...

Aug 13, 20255 min read

nihcas.hashnode.dev

Instruction Reordering: Your Code Doesn’t Always Run in the Order You Wrote It

When writing code, you naturally expect instructions to run one after the other in the exact order they appear. For example: x=1; y=2; You’d expect x = 1 to complete before y = 2 starts. But in reality, modern CPUs and compilers don’t always execute...

Aug 5, 20255 min read

nihcas.hashnode.dev

Blocking vs Non-blocking vs Asynchronous I/O

When a program performs I/O → like reading from a file or socket → two key questions arise: Does the program stop and wait for the data, or continue running? (Blocking vs Non-blocking IO) Does the program keep checking for the result, or get notifi...

Jul 30, 20254 min read

nihcas.hashnode.dev

Traditional IO vs mmap vs Direct IO: How Disk Access Really Works

In our earlier deep dive into Direct Memory Access (DMA), we explored how data can bypass the CPU to move efficiently between storage and memory. In this article, we will break down and compare three major approaches to disk access: Traditional (Buf...

Jul 20, 20253 min read

Sachin Tolay

About

Available for

Sachin Tolay's blogs

Recently published

From Sessions to JWTs: How Distributed Systems Reshaped Identity

Memory Models Explained: How Threads Really See Memory

Instruction Reordering: Your Code Doesn’t Always Run in the Order You Wrote It

Blocking vs Non-blocking vs Asynchronous I/O

Traditional IO vs mmap vs Direct IO: How Disk Access Really Works

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Sachin Tolay

About

Available for

Sachin Tolay's blogs

Recently published

From Sessions to JWTs: How Distributed Systems Reshaped Identity

Memory Models Explained: How Threads Really See Memory

Instruction Reordering: Your Code Doesn’t Always Run in the Order You Wrote It

Blocking vs Non-blocking vs Asynchronous I/O

Traditional IO vs mmap vs Direct IO: How Disk Access Really Works