GraphQL is highlighted as a flexible API query language designed for streamlined data querying, particularly beneficial in scenarios with complex schemas where only specific subsets of data are needed. Unlike REST APIs, where requests might retrieve all data from a record, GraphQL allows clients to select only the data they require, exemplified by queries extracting specific fields like country names, capitals, and languages. While this flexibility benefits the client by reducing unnecessary data processing, it presents challenges for server developers, such as unpredictable performance and caching difficulties, leading to a steep learning curve. GraphQL is recommended when clients need varied data consumption methods, although it requires more backend effort. The blog series concludes that API development should be tailored to specific business needs, with microservices enabling the use of different API models like gRPC, REST, and GraphQL within the same system.