When data required by client applications is spread across multiple microservices. The materialized view pattern should be used when the data required by client applications is spread across multiple microservices, and making multiple requests to access this data would be inefficient. This pattern can provide a faster and more efficient way to access the data that the client needs. 

https://medium.com/design-microservices-architecture-with-patterns/materialized-view-pattern-f29ea249f8f8#:~:text=Materialized%20View%20Pattern%20is%20recommend,data%20as%20a%20Read%20Model.