Azure API Management latency of over 5 seconds - azure-api-management

Question

We're using API Management to execute an always on function app that, in turn, is calling Azure Search. The function app responds within 100 ms (usually well under), but API Management intermittently takes 3 to 8 seconds to process. I've gone through the trace and found the delay is consistently in the backend step in which API Management is processing the results (sample trace for backend below). The returned data in this case is 664 bytes. Does anyone know what may cause this and, more importantly, how to remove this latency?
The Azure API Management instance, function app, and Azure Search are all in the same region.
"backend": [
{
"source": "forward-request",
"timestamp": "2018-10-11T13:33:54.0578250Z",
"elapsed": "00:00:00.0005890",
"data": {
"message": "Request is being forwarded to the backend service. Timeout set to 300 seconds",
"request": {
"method": "GET",
"url": "https://ommitted.azurewebsites.net/api/HollanderSearch/?hollander=125-222L&websiteId=1&retrieveAllProductNames=false&onlyRetrieveProductNames=true&numRecsToRetrieve =25&code=%2Fxu1iz0EimDFnOUvhDVaM4ZejfaW7umV3somaIDCeWJYI5RMIfNnNg%3D%3D&keyword=125-222L",
"headers": [
{
"name": "Ocp-Apim-Subscription-Key",
"value": "ommitted"
},
{
"name": "Postman-Token",
"value": "9e809f11-6e63-4422-8c3f-d61962cec6ac"
},
{
"name": "Cache-Control",
"value": "no-cache"
},
{
"name": "Accept",
"value": "*/*"
},
{
"name": "Accept-Encoding",
"value": "gzip,deflate"
},
{
"name": "User-Agent",
"value": "PostmanRuntime/7.3.0"
},
{
"name": "X-Forwarded-For",
"value": "omitted"
}
]
}
}
},
{
"source": "forward-request",
"timestamp": "2018-10-11T13:33:59.6717259Z",
"elapsed": "00:00:05.6045857",
"data": {
"response": {
"status": {
"code": 200,
"reason": "OK"
},
"headers": [
{
"name": "Pragma",
"value": "no-cache"
},
{
"name": "Transfer-Encoding",
"value": "chunked"
},
{
"name": "Content-Encoding",
"value": "gzip"
},
{
"name": "Vary",
"value": "Accept-Encoding"
},
{
"name": "Cache-Control",
"value": "no-cache"
},
{
"name": "Content-Type",
"value": "application/json; charset=utf-8"
},
{
"name": "Date",
"value": "Thu, 11 Oct 2018 13:33:59 GMT"
},
{
"name": "Expires",
"value": "-1"
},
{
"name": "Set-Cookie",
"value": "ARRAffinity=8065e5ea6c0774f598f30cd38416a122cd6afe1af34a15c7f6430e1a0fe9924c;Path=/;HttpOnly;Domain=omitted-dev.azurewebsites.net"
},
{
"name": "Server",
"value": "Microsoft-IIS/10.0"
},
{
"name": "X-Powered-By",
"value": "ASP.NET"
}
]
}
}
},
{
"source": "decompressor",
"timestamp": "2018-10-11T13:33:59.6717259Z",
"elapsed": "00:00:05.6045976",
"data": "Content-Encoding header with value `gzip` detected in message headers. Content re-compression may require to correctly apply content modification policies."
}
]