The Backend Engineering Show with Hussein Nasser

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 
⁃ ⁃ ⁃ ⁃ ⁃ 19:00 Multi-level Paging (Radix tree)
⁃ ⁃ 31:00 Huge Tables
⁃ ⁃ 33:00 TLB
⁃ ⁃ Summary

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 physical memory
Memory sharing
Allow more processes to run , unused go to disk
Numa, kernel can place memory near the cpu
12:00 VMA areas
Text/code 
Data 
BSS
Heap
Stack
19:50 Kernel mode
25:30 What is a Page fault?
30:30 First access page fault
33:00 Stack Expansion page fault
34:30 CoW page fault
38:00 Swap page fault
39:39 File backed page fault
40:29 Permission page fault 
45:30 Summary

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 GOAWAY frame. 

0:00 Intro
4:58 Why shutdown connection? 
6:46 HTTP/1.1 Graceful shutdown
12:26 Cost of HTTP/2 
17:40 HTTP/2 GoAWAY frame
23:40 Summary

Links
https://www.youtube.com/watch?v=fVKPrDrEwTI&t=1s 
https://chromium.googlesource.com/chromium/src/net/%2B/master/socket/client_socket_pool_manager.cc#76
https://issues.chromium.org/issues/40555364
https://issues.chromium.org/issues/40501721