In my opinion, the java.lang.OutOfMemoryError: Java heap space that you are experiencing in NiFi may not be due to a built-in memory leak as you say. This could be caused because of the result of the workload exceeding the allocated heap. With such a huge number of processors, 123 and large flowfiles (50 MB × 200), memory demand definitely will grow rapidly, and the 4 GB heap configured in bootstrap.conf may not be sufficient. In general, NiFi is designed to handle large data flows, but of course it requires proper tuning. You can try to decrease the memory usage by increasing the heap size (if hardware allows), adjusting processor concurrency so heavy processors don’t run in parallel, and configuring back pressure to limit queued flowfiles. All these can actually help with reducing memory pressure. Additionally, efficient use of NiFi’s repositories (content, flowfile, provenance) ensures less reliance on heap memory.  Following these optimisations can support your NiFi instance  to handle the workload more effectively and also to avoid frequent OutOfMemory errors. To know the different types of OutOfMemoryError and how to resolve them, you can refer to this blog: Types of OutOfMemoryError ... View more