Scaling Fundamentals
How systems grow under load — vertical vs horizontal scaling, why statelessness is the real enabler, load balancing from L4 to L7, consistent hashing, read/write scaling, the scale cube, and when the honest answer is "don't scale yet."
How systems grow: vertical vs horizontal scaling, statelessness as the enabler of horizontal scale, load balancing (L4/L7, consistent hashing), read/write scaling with replicas — and knowing when not to scale.