The Backend Engineering Show with Hussein Nasser

The infinite scroll in social media as we know it today is despised by all. But it always start as a bad idea. It originated as a result of UI change to relief the backend database from inefficient queries. I explore this in this episode of the backend engineering. 0:00 Intro1:00 Classic Paged results 6:23 Limitations of paging9:00 The scroll interface 12:00 How TikTok to infinite scroll 14:00 The...

An aws engineer discovered a 50% regression in postgres throughput while testing the new Linux 7.0 kernel. The cause turns out to be massive TLB and page faults exacerbated by Postgres process-based design. In this backend engineering show episode I dive deep into how this was discovered, the root cause and the possible fixes and workarounds. Intermediate and Advanced Backend Engineering Course Bu...

A discussion about why many engineers still love the struggle, the mistakes, and the process of figuring things out themselves. This is how we grow and get better and stronger. Letting AI do everything (even though it can’t) robs us this feeling.. 

I wrote a new book that has been in the works for years. It is called Root Cause , and it is for those who enjoy the art of backend engineering. Early in my career, 20 years ago, I built backend and database applications without fully grasping their inner mechanics. Performance issues, race conditions, bugs, and even data corruption often left me lost. Since that day, I resolved to truly understan...

In this video I introduce 5 different design patterns for building backend applications. Each mode explains how a socket listener is established, a connections are established and how threads and connections are managed to read, write and process requests.

Page tables provide the mapping between virtual memory and physical memory for each process. This means it needs to be as efficient and as fast as possible. I explore the inner workings of page tables in this episode. 0:00 Intro 2:00 Virtual Memory ⁃ ⁃ 8:00 MMU 10:00 Page Tables ⁃ ⁃ ⁃ ⁃ ⁃ ⁃ ⁃ 11:30 Single Table Byte Addressability   ⁃ ⁃ ⁃ ⁃ ⁃ ⁃ ⁃ ⁃ 16:00 Single Table Page addressability  ⁃ ⁃ ⁃ ⁃ ⁃...

Page faults occurs when the process tries to access a memory that isn’t backed by a physical page kernel raises a fault which loads a page. It happens on first access, stack expansion, COW, swap and much more. However it comes with a cost.  In this episode of the backend engineering show I dissect the need and the cost page faults in the kernel.  0:00 Intro  4:00 Virtual memory Abstraction of phys...

On October 19 2025 AWS experienced an outage that lasted over a day, 10 days later we finally got the root cause analysis and we know exactly what caused the DNS to fail0:00 Summary 5:30 How did Dynamo lost its DNS?13:41 EC2 Errors 16:16 Network Load Balancer ErrorsRCA here https://aws.amazon.com/message/101925/

There are cases where the backend may need to close the connection to prevent unexpected situations, prevent bad actors or simply just free up resources. Closing a connection gracefully allows clients and backends to clean up and finish any pending requests.  In this episode of the backend engineering show I discuss graceful connections in both HTTP/1.1 via the connection header and HTTP/2 via the...

Postgres 18 has been released with many exciting features such as UUIDv7, Over explain module, composite index skip scans, and the most anticipated asynchronous IO with worker and io_uring mode which I uncover in this show. Hope you enjoy it 0:00 Intro 1:30 Synchronous vs Asynchronous calls 3:00 Synchronous IO 6:30 Asynchronous IO 10:00 Postgres 17 synchronous io 17:20 The challenge of Async IO in...

Fundamentals of Operating Systems Course https://oscourse.winktls is brilliant. TLS encryption/decryption often happens in userland. While TCP lives in the kernel. With ktls, userland can hand the keys to the kernel and the kernel does crypto. When calling write, the kernel encrypts the packet and send it to the NIC.When calling read, the kernel decrypts the packet and handed it to the userspace....

If you are bored of contemporary topics of AI and need a breather, I invite you to join me to explore a mundane, fundamental and earthy topic. The CPU. A reading of my substack article https://hnasr.substack.com/p/the-beauty-of-the-cpu

This new PostgreSQL 17 feature is game changer. They know can combine IOs when performing sequential scan. Grab my database course https://courses.husseinnasser.com

No technical video today, just talking about the idea of discipline and consistency.

Fundamentals of Operating Systems Course This video is an overview of how the operating system kernel does socket management and the different data structures it utilizes to achieve that. timestamps 0:00 Intro 1:38 Socket vs Connections 7:50 SYN and Accept Queue 18:56 Socket Sharding 23:14 Receive and Send buffers 27:00 Summary

Polling is the ability to interrogate a backend to see if a piece of information is ready. It can introduce a chatty system and as a result long polling was born. In this video I explain the beauty of this design pattern and how we can push it to its limit. 0:00 Intro 0:45 Polling 2:30 Problem with Polling 3:50 Long Polling 8:18 Timeouts 10:00 Long Polling Benefits 12:00 Make requests into Long Po...

You get better as a software engineer when you go through these stages. 0:00 Intro  1:15 Understand a technology 7:07 Articulate how it works 15:30 Understand its’ limitations 19:48 Try to build something better 27:45 Realize what you built also has limitations 32:48 Appreciate the original tech as is Understand a technology   We use technologies all the time without knowing how it works. And it i...

Fundamentals of Operating Systems Course https://oscourse.win Very clever! We often call read/rcv system call to read requests from a connection, this copies data from kernel receive buffer to user space which has a cost. This new patch changes this to allow zero copy with notification. “Reading' data out of a socket instead becomes a “notification” mechanism, where the kernel tells userspace wher...

Cloudflare built a global cache purge system that runs under 150 ms. This is how they did it. Using RockDB to maintain local CDN cache, and a peer-to-peer data center distributed system and clever engineering, they went from 1.5 second purge, down to 150 ms. However, this isn’t full picture, because that 150 ms is just actually the P50. In this video I explore Clouldflare CDN work, how the old cor...

Fundamentals of Database Engineering udemy course https://databases.win MySQL has been having bumpy journey since 2018 with the release of the version 8.0. Critical crashes that made to the final product, significant performance regressions, and tons of stability and bugs issues. In this video I explore what happened to MySql, are these issues getting fixed? And what is the current state of MySQL...

Fundamentals of Operating Systems Course https://oscourse.win In this video I use strace a performance tool that measures how many system calls does a process makes. We compare a simple task of reading from a file, and we run the program in different runtimes, namely nodejs, buns , python and native C. We discuss the cost of kernel mode switches, system calls and pe 0:00 Intro 5:00 Code Explanatio...

Fundamentals of Operating Systems Course https://os.husseinnasser.com When do you use threads? I would say in scenarios where the task is either 1) IO blocking task 2) CPU heavy 3) Large volume of small tasks In any of the cases above, it is favorable to offload the task to a thread. 1) IO blocking task When you read from or write to disk, depending on how you do it and the kernel interface you us...

I am fascinated by how timeouts affect backend and frontend programming. When a party is waiting on something you can place a timeout to break the wait. This is useful for freeing resources to more critical processes, detecting slow operations and even avoiding DOS attacks. Contrary to common beliefs, timeouts are not exclusive to request processing, they can be applied to other parts of the front...

Learn more about database and OS internals, check out my courses  Fundamentals of database engineering https://databases.win   Fundamentals of operating systems https://oscourse.win This new PostgreSQL 17 feature is game changer. You see, postgres like most databases work with fixed size pages. Pretty much everything is in this format, indexes, table data, etc. Those pages are 8K in size, each pag...

Fundamentals of Operating Systems Course https://os.husseinnasser.com Why Windows Kernel connects slower than Linux I explore the behavior of TCP/IP stack in Windows kernel when it receives a RST from the backend server especially when the host is available but the port we are trying to connect to is not. This behavior is exacerbated by having both IPv6 and IPv4 and if the happy eye ball protocol...