Hazelcast: In-Memory Data Grid

// Java configuration
Config config = new Config();
config.getMapConfig("user-sessions")
  .setTimeToLiveSeconds(3600)
  .setMaxIdleSeconds(1800)
  .setEvictionConfig(new EvictionConfig()
    .setSize(1000)
    .setMaxSizePolicy(MaxSizePolicy.PER_NODE)
    .setEvictionPolicy(EvictionPolicy.LRU));

HazelcastInstance hz = Hazelcast.newHazelcastInstance(config);
IMap<String, User> userMap = hz.getMap("user-sessions");

// Store and retrieve data
userMap.put("user123", new User("John", "Doe"));
User user = userMap.get("user123");

// Near cache configuration for performance
config.getMapConfig("user-sessions")
  .setNearCacheConfig(new NearCacheConfig()
    .setInvalidateOnChange(true)
    .setTimeToLiveSeconds(60));

// Cache configuration with store integration
MapConfig cacheConfig = new MapConfig("product-cache")
  .setMapStoreConfig(new MapStoreConfig()
    .setClassName("com.example.ProductMapStore")
    .setEnabled(true)
    .setWriteDelaySeconds(5)
    .setWriteBatchSize(100))
  .setMaxIdleSeconds(300);

// Read-through pattern
public class ProductMapStore implements MapStore<String, Product> {
  private ProductRepository repository;
  
  @Override
  public Product load(String productId) {
    // Automatically loads from database if not in cache
    return repository.findById(productId);
  }
  
  @Override
  public void store(String key, Product product) {
    // Write-behind: batch writes to database
    repository.save(product);
  }
  
  @Override
  public Map<String, Product> loadAll(Collection<String> keys) {
    return repository.findAllById(keys);
  }
}

// Usage - cache handles database integration transparently
IMap<String, Product> productCache = hz.getMap("product-cache");
Product product = productCache.get("prod123"); // Auto-loads if missing