Slow server hello when setting up SSL handshake azure apim

Question

Slow server hello when setting up SSL handshake azure apim

Corne Hendrickx 0

We have several customers that complain about a slow server response when setting up a SSL handshake.

What we see is this:

Client send SSL HELLO.

Server SSL Hello response takes 10 or more seconds.

We can not figure out what this is causing.

In the wire shark trace we see that the server response takes this long.

Rakesh Mishra 3,625 Reputation points Microsoft External Staff Moderator

2025-12-01T09:36:01.64+00:00

Hi @Corne Hendrickx , following up to see if you had a chance to check my previous response and if it was helpful. Please do let me know if you're still facing the issue and need any further assistance on this.

1 answer

Your answer

Rakesh Mishra 3,625 Reputation points Microsoft External Staff Moderator

2025-12-01T09:36:01.64+00:00

Hi @Corne Hendrickx , following up to see if you had a chance to check my previous response and if it was helpful. Please do let me know if you're still facing the issue and need any further assistance on this.

Answer 1

Siddhesh Desai 650 Microsoft External Staff Moderator

Hi Corne Hendrickx,

Thank you for reaching out to Microsoft Q&A

In your APIM Instance > Can you visit > Diagnose & solve problems > Availability & Performance > And see if you can get an insight on why the API response is slow.

Refer: https://learn.microsoft.com/en-us/azure/api-management/diagnose-solve-problems#availability-and-performance

APIM’s SSL Hello timing is primarily influenced by the client’s path to your gateway hostname and the certificate chain it receives. Backend API slowness shows after the handshake, and APIM guidance recommends Inspector traces to confirm where time is spent. https://learn.microsoft.com/en-us/troubleshoot/azure/api-mgmt/availability/performance-hit-api-calls

Corne Hendrickx 0 Reputation points

2025-12-01T10:33:18.1633333+00:00

Hi Siddhesh Desai,

It does not solve my problem. I do not have any over load on components. Back-end is fast. Certificate for verification is loaded on azure APIM itself.

Still we see the slow handshake at our customers. My next step will be, creating a Vnet in front of azure APIM, to capture the network traffic of this customer and see if the delay starts in azure or if it is a result of his connection.

If you have any suggestions to check additionally, please let me know.

Share via

Slow server hello when setting up SSL handshake azure apim

1 answer

Your answer