Your application has memory leaks due to improper handling of cache objects. How would you optimize memory management using L1 and L2 garbage collection?

Memory leaks caused by cache objects usually occur when cached entries remain in memory longer than necessary. While garbage collectors reclaim unreachable objects, effective memory management requires proper cache design, eviction policies, and controlled object retention. In Java, the terms L1 and L2 are commonly associated with cache layers rather than garbage collection levels. A multi-level caching strategy combined with efficient GC tuning helps optimize memory usage and application performance.

Key Points: • Implement cache eviction policies such as LRU (Least Recently Used), TTL (Time To Live), or size-based eviction to prevent unbounded memory growth. • Use a small, fast L1 cache for frequently accessed data and a larger L2 cache for less frequently used data. • Configure and tune garbage collectors such as G1 GC, ZGC, or Shenandoah to efficiently reclaim unused memory and reduce pause times.

Example: In an e-commerce application, frequently accessed product details can be stored in an in-memory L1 cache, while less frequently used products reside in a distributed L2 cache such as Redis. When cache entries expire or become unused, they are removed, allowing the garbage collector to reclaim memory.

Code Example:

import java.util.LinkedHashMap;
import java.util.Map;

public class LRUCache<K, V>
        extends LinkedHashMap<K, V> {

    private final int maxSize;

    public LRUCache(int maxSize) {

        super(16, 0.75f, true);
        this.maxSize = maxSize;
    }

    @Override
    protected boolean removeEldestEntry(
            Map.Entry<K, V> eldest) {

        return size() > maxSize;
    }
}

Optimization Strategies: • Use bounded caches instead of unlimited caches. • Apply LRU, LFU, or TTL-based eviction policies. • Use WeakReference or SoftReference where appropriate. • Regularly monitor heap usage and cache size. • Analyze heap dumps using MAT or VisualVM. • Tune heap size and garbage collector settings based on workload patterns.

Interview Tip: A concise interview answer is: To prevent cache-related memory leaks, I implement bounded L1 and L2 caching with proper eviction policies such as LRU or TTL. I ensure obsolete cache entries are removed promptly, use appropriate reference types when needed, and tune garbage collectors like G1 GC or ZGC to efficiently reclaim unused memory while maintaining application performance.