The document discusses handling complex POST and PATCH requests in RESTful APIs. It describes a RESTful API called ProFIT that was created for a product fulfillment and information tracking system. The API has around 60 entities and 100 endpoints and supports GET, POST, PUT, PATCH requests. Examples are provided for GET requests to retrieve orders and their items, as well as POST and PATCH requests. The benefits of using data transfer objects and serialization libraries like JMSSerializerBundle and SimpleThingsFormSerializerBundle are covered. The presentation also discusses validation, authentication, testing, and best practices for building RESTful APIs with Symfony.