Real-time data platforms promise instant insights, but at scale, they often fail in unexpected and expensive ways. In large IoT ecosystems processing hundreds of GBs of data and ingesting over 100 million events per day across multiple real-time pipelines, even well-designed systems begin to show cracks. This session explores real-world production challenges such as query latency on billion-row datasets, ineffective partitioning and indexing strategies, data skew, hot partitions, and pipeline backpressure in high-throughput environments. It highlights why indexed queries can still take seconds, how traditional design patterns break under extreme scale, and how scaling decisions directly impact the balance between cost and performance. The talk also covers practical solutions, architectural trade-offs for real-time systems, techniques to improve pipeline reliability and observability, and approaches to optimize performance under continuous load. Drawing from hands-on experience operating large-scale IoT data platforms, this session offers battle-tested insights and actionable guidance for building systems that not only scale efficiently but also remain resilient under real-world pressure.