Proxy, @Transactional Pitfalls & Internals

Private methods are invisible to the CGLIB proxy, self-invocation via this bypasses the proxy, @Async threads lose ThreadLocal context, and the fix for all proxy issues is to call through a separate bean.

BeanPostProcessor wraps every bean during creation (AOP proxies are built here), @EventListener decouples services with in-process events, SmartLifecycle orders startup and shutdown, virtual threads scale I/O cheaply, and Spring Batch processes data in fault-tolerant chunks.