In the final installment of the series "The Cost of Not Knowing MongoDB," the article explores advanced MongoDB design patterns to enhance application performance, focusing on reducing document size to tackle disk throughput bottlenecks. Building upon previous optimizations, the article introduces a dynamic schema approach, which replaces arrays with documents and leverages field names to encode information, resulting in a notable reduction in storage requirements. Despite these improvements, the performance gains were less than anticipated due to memory and cache limitations, suggesting the bottleneck was not disk-related. Consequently, the article proposes increasing the bucketing interval from month to quarter in the subsequent application revision, appV6R1, to decrease index size and improve performance further. The implementation retains most of the code from appV6R0, with modifications to the _id field and items document. The performance evaluation of appV6R1, which buckets data by quarter, shows significant improvements in document and data size compared to appV5R3, with further efforts recommended to optimize index size relative to available memory.