horizontal scaling (13:00 - 21:00)
load balancing & caching (21:00 – 29:00)
shared session state (29:00 – 34:00)
RAID (36:00 – 40:00)
shared storage tech (42:00)
database replication (43:00)
load balancing tech (44:00 – 45:00)
session affinity (46:00 – 51:00)
in-memory caching (59:00 – 1:00)
data replication – active:passive (1:11 - 1:14), active:active (1:16 - 1:21)
partitioning (1:21 – 1:34)
data center redundancy (1:33 – 1:39)
security (1:39 – 1:44)

I'm legitimately terrified that I'll be in a system design interview, they'll ask me a question, and I'll immediately turn and ask, "Axel?"

Somebody needs to add a load balancer in front of Axel, all requests are being routed to Axel (he is still handling them pretty well though) :P

Nobody:
Literally Nobody:
David: Axel?

Plot Twist : Axel, Jack and Isaac are the only kids in class.

Its been 7 years for me. I loved it then and still do. The entire course launched my career!

Where is Axel today in 2024?

What I learned with all of this is that, if you have a problem in your system, just add a load balancer, if the problem persist, add more load balancers, if the problem is on the load balancer itself, add a load balancer to the load balancer.

This is a piece of history for the modern internet. He mentioned AWS EC2 like a VPS, 12 years have passed but the internet world has completely changed.

come here from The System Design Primer repo

It's 2026 and what David is teaching here hasn't changed one bit. It's so fundamental that I tend to reference this lecture to friends and colleagues all the time.

I picture Axel just sitting there holding his hand up the entire lecture

Can't believe a 12 year old content with such a rich knowledge explained in so much depth and detail , really loved your style of teaching with such a engagement and detailed process rather than jumping to conclusion discussing all possible flows and suggesting solution to solve them. This content is gold.
Thank you David Malan and Jorge Scott

This guy has such a great Socratic teaching style! At first I was annoyed by the constant questioning, but then I started participating myself (even though I didn't watch the rest of the course) and had a lot more fun!

In this class, Axel is the anti-Jon Snow. He knows everything!

I don't comment usually but as a junior software developer this video was breath taking. For the first time in my life I wanted to be in a class and discuss about this level of theoric class. Thanks David you made me remember I love what I do!

Axel is unstoppable!!

As a tenured engineer, this was really good to listen to (even if I knew most of it from experience). It also made me a bit jealous of the quality of education at Harvard.

Axel is wasting his money on this course

Somehow i learnt one thing - Axel knows everything!