The Backend Engineering Show with Hussein Nasser

In this episode of the backend engineering show, I discuss the log4j vulnerability (CVE-2021-44228 also known as log4shell) that took the Internet by storm. 0:00 Intro 1:00 log4j 5:30 How the attack started 11:00 Attack with DNS 17:00 Remote Code Execution 23:00 Remedy 31:00 Scanning References https://nvd.nist.gov/vuln/detail/CVE-2021-44228 https://youtu.be/oC2PZB5D3Ys 🧑‍🏫 Courses I Teach https://husseinnasser.com/courses Become a Member on YouTube https://www.youtube.com/channel/UC_ML5xP23TOWKUcc-oAE_Eg/join 🔥 Members Only Content https://www.youtube.com/playlist?list=UUMO_ML5xP23TOWKUcc-oAE_Eg

In this episode of the backend engineering show taken from my udemy Q&A I discuss the reasons behind Postgres HOT Optimization or heap only tuple. 

Postgresql database implements MVCC by creating a new row version for any update/delete/or insert. While this is a sound implementation to support concurrent transactions reading old version of the rows, it does have some side effects and this is what I want to discuss in this episode of the backend engineering show. 0:00 Intro 1:00 Postgres MVCC design 6:42 MVCC on other databases 11:15 Side-effects of Row-versioning 17:00 Postgres HOT optimization 19:50 How Index bloat affects Performance 24:20 How Postgres 14 Addresses index bloat Cards: 14:12 b-tree https://www.youtube.com/watch?v=a1Z40OC553Y Resources https://www.postgresql.org/docs/14/btree-implementation.html#BTREE-DELETION

Head to https://database.husseinnasser.com to get a discount coupon for my introduction to database engineering.   In this video, I answer some of your questions on the Introduction to Database Engineering Course.

head to https://database.husseinnasser.com to get a discount coupon for my Introduction to Database Engineering course In this episode of the backend engineering show, I’ll discuss three instances where indexes can be useless and might add overhead to your operations. Let us discuss. 0:00 Intro 1:34 What is an Index? 4:00 The Cost of Indexes 6:40 Most values are the similar 13:00 WHERE UPPER(NAME)=‘RICK’ 17:10 Composite Index 23:00 How do I know if I’m using an Index

The cost of a long-running update transaction that eventually failed in Postgres (or any other database for that matter. In Postgres, any DML transaction touching a row creates a new version of that row. if the row is referenced in indexes, those need to be updated with the new tuple id as well. There are exceptions with optimization such as heap only tuples (HOT) where the index doesn’t need to be updated but that doesn’t always happens. If the transaction rolls back, then the new row versions created by this transaction (millions in my case) are now invalid and should NOT be read by any new transaction. You have two solutions to address this, do you clean all dead rows eagerly on transaction rollback? Or do you do it lazily as a post process? Postgres does the lazy approach, a command called vacuum which is called periodically Postgres attempts to remove those dead rows and free up space in the page. Whats the harm of leaving those dead rows in? Its not really correctness issues at all, in fact transactions know not to read those dead rows by checking the state of the transaction that created them. This is however expensive, the check to see of the transaction that created this row is committed or rolled-back. Also the fact that those dead rows live in disk pages with alive rows makes an IO not efficient as the database has to filter out dead rows. For example, a page may have contained 1000 rows, but only 1 live row and 999 dead rows, the database will make that IO but only will get a single row of it. Repeat that and you end up making more IOs. More IOs = slower performance. Other databases do the eager approach and won’t let you even start the database before rolling back is successfully complete, using undo logs. Which one is right and which one is wrong? Here is the fun part! Nothing is wrong or right, its all decisions that we engineers make. Its all fundamentals. Its up to you to understand and pick. Anything can work. You can make anything work if you know what you are dealing with. If you want to learn about the fundamentals of databases and demystify it check out my udemy course  https://database.husseinnasser.com

In this episode of the backend engineering show, I’ll discuss all HTTPS/TLS binding options in Microsoft IIS and also explain why every web server and reverse proxy should have some of these fine level control. Chapters 0:00 Intro 1:00 Require Server Name Indication (SNI) 5:00 Disable TLS 1.3 Over TCP 8:30 Disable Legacy TLS 10:00 Disable OCSP Stapling 12:00 Disable QUIC 14:30 Disable HTTP/2 17:30 Certificate Get my database course https://database.husseinnasser.com Get my NGINX course https://nginx.husseinnasser.com Get my Python on the Backend course https://python.husseinnasser.com

I get a lot of emails asking me to talk about graph databases, so I want to start researching them, but I wanted to give you guys the framework of how I think about any databases to defuse any “magic” that might be there. In this video, I discuss what constrains a database and how the use cases try to work around them. 0:00 Intro 1:50 What constrains a database? 4:00 Indexing Techniques 5:30 Storage Engines - Row-Store 9:00 Columnar Databases 12:00 Graph use cases 16:00 Graph Storage Engines Learn the fundamentals of databases, grab my my Introduction to Database Engineering udemy course here for a discount coupon https://database.husseinnasser.com 🧑‍🏫

Certificates contain useful metadata including the public key, domain name, signature, etc. However, the private key can be leaked which causes the certificate to be invalid/dangerous to keep around. In that particular situation, we need a mechanism to revoke certificates and that is what I’m going to discuss in this show. 0:00 Intro 0:30 Why Certificates 12:00 Certificates can go bad 14:50 Certificate Revocation Lists (CRLs) 18:30 OCSP (Online Certificate Status Protocol) 20:40 OCSP Stapling 24:30 Best certificates are short 26:30 Summary Become a Member on YouTube https://www.youtube.com/channel/UC_ML5xP23TOWKUcc-oAE_Eg/join 🔥 Members Only Content https://www.youtube.com/playlist?list=UUMO_ML5xP23TOWKUcc-oAE_Eg Support my work on PayPal https://bit.ly/33ENps4

In this episode, I go through the Facebook detailed article regarding their October 4th, 2021 outage and discuss it in length. enjoy Facebook blog: https://engineering.fb.com/2021/10/05/networking-traffic/outage-details/ 0:00 Introduction on Facebook Networking Architecture 12:00 The Cause of the Outage 17:00 What’s DNS 23:00 DNS Servers disabled BGP ads 27:00 Could the outage have been prevented? 32:00 Why did it take so long? 38:00 Why you can’t just flip everything on 41:30 Summary 🧑‍🏫 Courses I Teach https://database.husseinnasser.com https://nginx.husseinnasser.com https://python.husseinnasser.com Become a Member on YouTube https://www.youtube.com/channel/UC_ML5xP23TOWKUcc-oAE_Eg/join 🔥 Members Only Content https://www.youtube.com/playlist?list=UUMO_ML5xP23TOWKUcc-oAE_Eg Support my work on PayPal https://bit.ly/33ENps4 🏭 Backend Engineering Videos in Order https://backend.husseinnasser.com 💾 Database Engineering Videos https://www.youtube.com/playlist?list=PLQnljOFTspQXjD0HOzN7P2tgzu7scWpl2