The Split Strategy: How to Write XLSX Files Fast Without Sacrificing Correctness

Large-scale XLSX generation is a persistent bottleneck in data processing. Developers face a false choice: Apache POI ensures correctness but with severe performance penalties, while hand-rolled solutions offer speed at the cost of maintaining complex OOXML compliance independently. This hybrid approach eliminates that trade-off by letting POI handle file integrity and StringBuilder handle high-throughput cell writes—delivering both correctness and performance.