Hibernate Level 1 caching : ( default ) session caching. This is for the particular instance of the session

Hibernate Level 2 caching : session Factory caching. All the sessions will have same caching

Post | LinkedIn

What is Cache?
-> Cache is a temporary fast-access storage used to store frequently accessed data so that repeated expensive operations can be avoided.

-> As we know that hitting each request to DB is really very cost effective operation, so cache will reduce database load, slashing latency, and improving application performance.

📌 Instead of hitting DB / API / Disk every time, we return data from cache.

1️⃣  Where Do We Use Cache ? (Real-Time Examples):
🔹 User profile data
🔹 Product catalog
🔹 Configuration data
🔹 Authentication & authorization data
🔹 Search results
🔹 API responses.

2️⃣ Types of Cache :
🔹In-Memory Cache :
1. Stored inside application memory
2. Very fast
3. Data lost on restart
Examples: HashMap, Caffeine.

🔹Distributed Cache
1. Shared across multiple services
2. Highly scalable.
Examples: Redis, Memcached.
📌 Used in microservices & cloud systems

🔹Client-Side Cache
1. used in browser / mobile app.
2.Reduces server calls.

3️⃣  Cache Levels:
🟢 L1 Cache:
1.Closest to application
2.Fastest
3.Limited size
🔵 L2 Cache:
1.Shared across services
2.Slower than L1 but scalable.

4️⃣ Cache Consistency Problem:
❌ Cache data can become stale
✔ Solution:
✅ providing TTL (Time To Live)
✅ Cache invalidation
✅ Event-based updates.

5️⃣ How Cache Works (Simple Flow):

Client → Application → Cache
↓ (miss)
Database

✔ Cache Hit → return data
✔ Cache Miss → fetch from DB → store in cache → return data.

6️⃣Cache in Spring Boot :

𝐄𝐧𝐚𝐛𝐥𝐞 𝐂𝐚𝐜𝐡𝐞:
@EnableCaching
@SpringBootApplication
public class App { }

𝐔𝐬𝐞 @𝐂𝐚𝐜𝐡𝐞𝐚𝐛𝐥𝐞 :
@Cacheable("products")
public Product getProductById(Long id) {
  return productRepository.findById(id).get();
}
✔ First call → DB
✔ Next calls → Cache.

𝐔𝐩𝐝𝐚𝐭𝐞 𝐂𝐚𝐜𝐡𝐞:
@CachePut(value = "products", key = "#product.id")
public Product updateProduct(Product product) {
  return productRepository.save(product);
}

𝐑𝐞𝐦𝐨𝐯𝐞 𝐂𝐚𝐜𝐡𝐞:
@CacheEvict(value = "products", key = "#id")
public void deleteProduct(Long id) {
  productRepository.deleteById(id);
}

7️⃣ Cache Providers in Spring Boot:
☑️ Caffeine (in-memory).
☑️Redis (distributed – most used)
☑️Hazelcast.
📌 Redis is preferred for microservices.

8️⃣ Cache in Microservices (Real-Time)
✔ Each service uses Redis
✔ Reduces DB load
✔ Improves API latency
✔ Supports horizontal scaling.
Example:
Product Service → Redis → Database.