Scenario A: PDF
- User will select PDF to download from Mobile catalog, mobile will make an API call to Gateway, Gateway will route/download the PDF from backend system and send the file to mobile.
Scenario B: Video
- User will select video to download from Mobile catalog, mobile will make an API call to Gateway, Gateway will route/download the video from backend system and send the file to mobile.
Scenario C: HTML 5
- User will click on Performance Dashboard button in mobile, mobile will make an API call to Gateway, Gateway will route the call tol CRM backend system (HTML 5 page) and response to mobile.
The gateway should be able to handle scenarios A and C. I have seen cases where pdfs and HTML pages are forwarded through the gateway.
I do not know about scenario B. Web Video is usually handled via streaming and not a request-response logic.
You should also keep in mind that the gateway will try to buffer the response in memory before it forwards it to the client. This can severely affect performance, especially with large files.
You can use the information in knowledge base article TEC0000001358, titled "API gateway: Optimizing for Large Files and Messages" found at http://www.ca.com/us/support/ca-support-online/product-content/knowledgebase-articles/tec0000001358.aspx.Also, the Configure Message Streaming Assertion - CA Technologies Documentation might be of use to you.
The gateway should be able to handle video as a stream. There is an assertion to configure message streaming so the gateway will not try to buffer the response first. This can also be used for large files.