عرض عملي: ذاكرة Caffeine مؤقتة محلية مع مقاييس

خطوة بخطوة

1. Add the Caffeine dependency and build a Cache<Long, ProductDto> with maximumSize(1000), expireAfterWrite(5, MINUTES), and recordStats().
2. Wrap findProduct(id): cache.get(id, this::loadFromDb).
3. Expose cache.stats() through Micrometer (hit count, miss count, load time).
4. Generate load with a small script; show the hit ratio rising after warm-up.
5. Planned mistake: cache the per-customer discounted price by product id only; a second customer sees the first customer's price. Fix: cache the shared base price and apply the discount afterwards, or include the customer tier in the key.
6. Verify Caffeine version and Micrometer binding names before recording.

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