The API Gateway has a default mediation flow for the API invocation requests that it receives. You can extend this default mediation flow to do additional custom mediation for the messages in the API Gateway. An extension is provided as a synapse mediation sequence. You design all sequences using a tool like WSO2 Developer Studio and then store the sequence in the Gateway's registry.
Please note that following mediators are not usable within custom sequences since they are not supported by API Gateway custom medications.
Let's see how to create a custom sequence using WSO2 Developer Studio and then deploy and use it in your APIs.