How can developers improve the performance of complex queries used by Dynamics 365 Finance and Operations reports?

Report performance in Dynamics 365 Finance and Operations should be treated as a data-access and report-design problem, not simply as an issue with the report itself. When a report becomes slow, developers should first identify where the time is being spent: query execution, joins, filtering, data retrieval, report processing, or rendering. Microsoft guidance emphasises appropriate data modelling, indexes, query design and avoiding unnecessary data retrieval; report design should also follow the optimisation patterns supported by the reporting engine.

A practical investigation should begin with the query. Ask whether the query retrieves only the required fields, whether filters can be applied efficiently, whether joins are appropriate, and whether the underlying tables have suitable indexes. In X++, developers should be particularly careful with inefficient data access patterns such as retrieving unnecessary columns or repeatedly querying the database inside loops. Microsoft also cautions that index hints should be used sparingly because forcing an inappropriate index can actually reduce performance.

A useful optimisation mindset is:

Slow Report
    |
    +---- Query Design
    |       |
    |       +---- Filters
    |       +---- Joins
    |       +---- Fields
    |
    +---- Data Model
    |       |
    |       +---- Indexes
    |       +---- Relationships
    |
    +---- Report Design
    |       |
    |       +---- Aggregation
    |       +---- Filtering
    |
    +---- Data Volume
            |
            +---- Current volume
            +---- Future growth

For working professionals, the key lesson is do not optimise based only on a developer workstation with a small dataset. A query that performs well with 10,000 records may behave very differently with millions of records. Test with representative data volumes and investigate the generated SQL/query execution behaviour rather than guessing.

For freshers, this is an important interview distinction: "I added an index" is not a complete performance strategy. A stronger answer explains which access pattern the index supports, what filtering and joining occurs, how the query behaves at scale, and how the change was measured.