A common issue in long-running Node.js applications is memory growth over time, which often points to a memory leak. This happens when objects that are no longer needed aren’t properly garbage collected because they’re still being referenced somewhere in your code. To debug memory leaks, you can use tools like `heapdump`, `clinic`, or Node.js’s built-in inspector to take memory snapshots and analyze the heap. The goal is to find objects that shouldn’t exist but persist in memory. Memory leaks can come from event listeners not being properly removed, global variables, or improper caching mechanisms. By analyzing memory usage patterns and understanding how your app manages object references, you can pinpoint the leak and optimize memory usage.