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. This mode still taxes the host’s CPU of course, so there is another mode where the kernel offloads th...
Jun 13, 2025•23 min
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
May 09, 2025•10 min
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
Apr 18, 2025•28 min
No technical video today, just talking about the idea of discipline and consistency.
Apr 11, 2025•10 min
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
Apr 04, 2025•31 min
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 Polling 17:36 Request Resumption 21:40 Summary
Dec 06, 2024•29 min
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 is ok not knowing how things work if interests isn’t there. But when there is interest to understand how...
Nov 01, 2024•39 min
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 where the data is.” This kernel patch enables zero copy from the receive queue. https://lore.kernel.org/...
Oct 25, 2024•18 min
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 core-based centralized quicksilver, lazy purge work compared to the new coreless, decentralized active ...
Oct 18, 2024•1 hr 2 min
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 at the end of 2024. 0:00 Intro 2:00 MySQL 8.0 vs 5.7 Performance 11:00 Critical Crash in 8.0.38, 8.4...
Sep 28, 2024•29 min
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 Explanation 6:30 Python 9:30 NodeJS 12:30 BunJS 13:12 C 16:00 Summary
Sep 20, 2024•21 min
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 used, the write might be blocking. This means the process that executes the IO will not be allowed to ...
Sep 13, 2024•31 min
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 frontend-backend communications. Let us explore this briefly. 0:00 Intro 2:30 Connection Timeout 5:00 Req...
Sep 07, 2024•25 min
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 page will have the rows, or index tuples and a fixed header. The pages are just bytes in files and they ar...
Sep 02, 2024•28 min
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 is in place where IPv6 is favorable. 0:00 Intro 0:30 Fundamentals TCP/IP 3:00 Unreachable Port Behav...
Aug 30, 2024•37 min
In this episode of the backend engineering show I describe an interesting bug I ran into where the web server ran out of ephemeral ports causing the system to halt. 0:00 Intro 0:30 System architecture 2:20 The behavior of the bug 4:00 Backend Troubleshooting 7:00 The cause 15:30 Ephemeral ports on loopback
Aug 25, 2024•20 min
Fundamentals of Operating Systems Course https://os.husseinnasser.com Linux I/O expert and subsystem maintainer Jens Axboe has submitted all of the IO_uring feature updates ahead of the imminent Linux 6.10 merge window. In this video I explore this with a focus on what zerocopy. 0:00 Intro 0:30 IO_uring gets faster 2:00 What is io_uring 7:00 How Normal Copying Work 12:00 How Zero Copy Works 13:50 ZeroCopy and TLS https://www.phoronix.com/news/Linux-6.10-IO_uring https://lore.kernel.org/io-uring/...
May 20, 2024•17 min
Fundamentals of Operating Systems Course https://oscourse.win Looks like fedora is compiling cpython with the -o3 flag, which does aggressive function inlining among other optimizations. This seems to improve python benchmarks performance by at most 1.16x at a cost of an extra 3MB in binary size (text segment). Although it does seem to slow down some benchmarks as well though not significantly. O1 - local register allocation, subexpression elimination O2 - Function inlining only small functions ...
May 07, 2024•29 min
https://oscourse.win Allegro improved their Kafka produce tail latency by over 80% when they switched from ext4 to xfs. What I enjoyed most about this article is the detailed analysis and tweaking the team made to ext4 before considering switching to xfs. This is a classic case of how a good tech blog looks like in my opinion. 0:00 Intro 0:30 Summary 2:35 How Kafka Works? 5:00 Producers Writes are Slow 7:10 Tracing Kafka Protocol 12:00 Tracing Kernel System Calls 16:00 Journaled File Systems 21:...
Apr 29, 2024•34 min
Get my backend course https://backend.win Google submitted a patch to Linux Kernel 6.8 to improve TCP performance by 40%, this is done via rearranging the tcp structures for better cpu cache lines, I explore this here. 0:00 Intro 0:30 Google improves Linux Kernel TCP by 40% 1:40 How CPU Cache Line Works 6:45 Reviewing the Google Patch https://www.phoronix.com/news/Linux-6.8-Networking https://lore.kernel.org/netdev/20231129072756.3684495-1-lixiaoyan@google.com/ Discovering Backend Bottlenecks: U...
Mar 05, 2024•14 min
0:00 Intro 2:00 File System Block vs Database Pages 4:00 Torn pages or partial page 7:40 How Oracle Solves torn pages 8:40 MySQL InnoDB Doublewrite buffer 10:45 Postgres Full page writes
Feb 29, 2024•16 min
Get my backend course https://backend.win Cloudflare has announced they are opening sources Pingora as a networking framework! Big news, let us discuss 0:00 Intro 0:30 Reasons why Cloudflare built Pingora? 3:00 It is a framework! 7:30 What in Pingora? 11:50 Security in Pingora 13:45 Multi-threading in Pingora 21:00 Customization vs Configuration 25:00 Summary https://blog.cloudflare.com/pingora-open-source/?utm_campaign=cf_blog&utm_content=20240228&utm_medium=organic_social&utm_sour...
Feb 28, 2024•31 min
https://backend.win https://databases.win I’m a big believer that database systems share similar core fundamentals at their storage layer and understanding them allows one to compare different DBMS objectively. For example, How documents are stored in MongoDB is no different from how MySQL or PostgreSQL store rows. Everything goes to pages of fixed size and those pages are flushed to disk. Each database define page size differently based on their workload, for example MongoDB default page size i...
Feb 19, 2024•45 min
In this video I explore the type of languages, compiled, garbage collected, interpreted, JIT and more.
Feb 19, 2024•18 min
I talk about default values and how PostgreSQL 14 got slower when a default parameter has changed. Mike's blog https://smalldatum.blogspot.com/2024/02/it-wasnt-performance-regression-in.html
Feb 18, 2024•12 min
Background writing is a process that writes dirty pages in shared buffer to the disk (well goes to the OS file cache then get flushed to disk by the OS) I go into this process in this video
Feb 16, 2024•9 min
Fragmentation is a very interesting topic to me, especially when it comes to memory. While virtually memory does solve external fragmentation (you can still allocate logically contiguous memory in non-contiguous physical memory) it does however introduce performance delays as we jump all over the physical memory to read what appears to us for example as contiguous array in virtual memory. You see, DDR RAM consists of banks, rows and columns. Each row has around 1024 columns and each column has 6...
Jan 29, 2024•39 min
In this video I explore the hidden costs of sending a request from the frontend to the backend Heard https://medium.com/@hnasr/the-journey-of-a-request-to-the-backend-c3de704de223
Dec 13, 2023•13 min
Fundamentals of Database Engineering udemy course (link redirects to udemy with coupon) https://database.husseinnasser.com Why create Index blocks writes In this video I explore how create index, why does it block writes and how create index concurrently work and allow writes. 0:00 Intro 1:28 How Create Index works 4:45 Create Index blocking Writes 5:00 Create Index Concurrently
Oct 28, 2023•13 min
HTTP/3 is getting popular in the cloud scene but before you migrate to HTTP/3 consider its cost. I explore it here. 0:00 Intro HTTP/3 is getting popular 3:40 HTTP/1.1 Cost 5:18 HTTP/2 Cost 6:30 HTTP/3 Cost https://blog.apnic.net/2023/09/25/why-http-3-is-eating-the-world/
Oct 05, 2023•14 min
