Power BI development company handle big data by using techniques like incremental refresh, DirectQuery, and aggregations to optimize performance. They connect Power BI with data lakes and cloud storage solutions, such as Azure, to manage large datasets. DirectQuery allows real-time querying of massive datasets without loading them into memory, ensuring faster processing times. Aggregations are used to summarize large datasets, improving report performance without losing data granularity. These companies design scalable solutions that can handle growing data volumes, ensuring that businesses can continue to access and analyze data efficiently as it expands.

DAX (Data Analysis Expressions) is crucial for Power BI developers because it allows them to create powerful calculations, such as calculated columns, measures, and aggregations. With DAX, Power BI developers can write custom formulas that enhance data analysis and help users extract valuable insights from reports. It enables advanced business logic, such as year-over-year comparisons, running totals, and time-intelligent calculations, making the dashboards and reports more dynamic. A strong understanding of DAX is essential for creating customized data models and performing complex analysis that goes beyond standard Power BI functionality.