Each layer depends on the one below it. Infrastructure patterns are implementations of algorithms. System designs are compositions of infrastructure patterns. Code architecture governs how system designs are expressed in code. Leadership determines which systems get built and how. Product strategy determines what value those systems deliver.
Each layer depends on the one below. More importantly, the same patterns appear at every layer. A queue at the mathematical level is FIFO ordering. At the algorithm level it enables BFS traversal. At the infrastructure level it is a Kafka topic. At the system level it is the fan-out mechanism in a news feed. At the code level it is an event emitter. At the leadership level it is the async handoff between teams. The word “queue” means something at every layer — and understanding all of them deepens your understanding of each.