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01From source to running codeBytecode, loading, the JIT

02Objects and typesHeap, collectors, generics, collections

03Many things at onceMemory model to virtual threads

04Next: system designSame ideas, at service scale

BulkheadLibrary ↗One shared thread pool for every kind of work is a single point of exhaustion. Give each dependency its own executor.

BackpressureLibrary ↗A ThreadPoolExecutor's queue is a buffer. Bound it and choose a rejection policy, or a slow dependency fills your heap.

TimeoutLibrary ↗CompletableFuture.orTimeout and a deadline on every blocking call: the same idea, between services.

01From source to running codeBytecode, loading, the JIT0/4
02Objects and typesHeap, collectors, generics, collections0/5
03Many things at onceMemory model to virtual threads0/3
04Next: system designSame ideas, at service scale

Everything here is about Java 21, the current long-term-support release. Where a behaviour belongs to HotSpot (the JVM in OpenJDK and Oracle's JDK) rather than to the Java Language Specification or the JVM Specification, the topic says so.

Where this path leads

Spring Boot: how a request becomes a response →What Spring Boot does between an HTTP request arriving and a response leaving: the container that builds your objects, the proxies that wrap them, the threads, transactions and connections each request borrows, and how to see and test it all.

Java: how the JVM runs your code

The map

Where this path leads