Kinesis Data Firehose's Hidden Partition Key Ceiling

AWS Kinesis Data Firehose imposes an undocumented limit of 1000 active partition keys that can silently break production pipelines and cause mysterious failures. Teams often overlook this constraint while focusing on traditional shard and throughput limits, leading to hard-to-diagnose performance issues. Understanding this hidden limitation is essential for building reliable real-time data pipelines at scale.