---
title: "AOP, events, scheduling, and caching"
chapter: "11"
---

# AOP, events, scheduling, and caching

Spring adds cross-cutting behavior around beans through proxies and supports
events, tasks, schedules, and cache abstractions.

## AOP

Aspect-oriented programming is useful for concerns applied consistently across
many methods: transactions, security, metrics, tracing, or narrowly defined
logging. A pointcut selects join points; advice runs before, after, or around
them.

Avoid hiding core business flow in aspects. If reading the method cannot reveal
that an order is published or a fee is charged, the design is surprising.

## Events

Application events decouple in-process components. By default, listeners run in
the publisher's thread. `@TransactionalEventListener` can bind handling to a
transaction phase. In-process events disappear if the process crashes; use a
durable broker/outbox for cross-service guarantees.

## Scheduling and async

`@Scheduled` triggers recurring work. In multiple replicas, every replica may
run it unless coordination exists. `@Async` uses an executor; configure pool
size, queue, rejection, context, and exception handling.

## Caching

`@Cacheable` can avoid repeated work, but every cache needs a key, TTL,
invalidation, maximum size, consistency expectation, and failure behavior.

## Feynman check

A proxy is a gate adding checks. An event is a bell inside one building. A
message broker is a postal service between buildings. A cache is a whiteboard
copy that can become stale.