Teams message extension timing out when calling external API during query

Question

On a custom Teams message extension that triggers an external API call during the composeExtension/query event, but I’m running into an issue where the request intermittently times out inside Teams even though the same API call works reliably when tested directly from Postman or using my bot endpoint outside Teams.

I’m using Bot Framework SDK (Node.js) with an Azure Function backend, and logs show that the bot receives the invoke request but sometimes never completes the round-trip back to Teams before the 5-second timeout. I’ve already tried reducing payload size, enabling App Insights logging, and moving the API call to a proxy layer, but the behavior is still inconsistent.

Answer 1

When dealing with timeouts in a Teams message extension, especially during external API calls, it's important to consider the following factors:

1. Timeout Duration: Teams has a strict timeout limit of 5 seconds for responding to the composeExtension/query requests. If your API call takes longer than this, Teams will terminate the request, resulting in a timeout error.
2. Performance Optimization: Since you've already tried reducing the payload size and moving the API call to a proxy layer, consider further optimizing your API call. This could involve caching responses, optimizing the backend processing time, or simplifying the data being returned.
3. Asynchronous Processing: If possible, consider implementing an asynchronous pattern where the Teams extension can respond immediately (e.g., with a loading indicator) and then follow up with the actual data once the API call completes. This way, you can avoid hitting the strict timeout limit.
4. Monitoring and Logging: Since you mentioned enabling App Insights logging, ensure that you are capturing detailed logs around the API call duration. This will help you identify any bottlenecks or issues that might be causing the delays.
5. Network Latency: Sometimes, network issues can cause delays in the API response. Ensure that your Azure Function and the external API are in the same region to minimize latency.

By addressing these areas, you may be able to reduce the occurrence of timeouts and improve the reliability of your Teams message extension.

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References:

• Set Timeout when making external calls in a plug-in
• Troubleshoot your Microsoft Teams app

Answer 2

Hi Doumbia

Thank you for reaching out to Microsoft Q&A forum

As far as I know, the root cause of this behavior is Search‑based message extensions are synchronous: when a user types or submits a query, Teams sends an composeExtension/query invoke and expects HTTP 200 within five seconds; if you miss that SLA, the client drops the request and shows “Unable to reach app.” This deadline is not configurable. Timeouts typically occur when the backend experiences cold‑start latency or network/TLS overhead (common on serverless plans), or when the extension spends too long building/returning results. These conditions explain why your direct tests succeed (no strict client SLA and a warmed host) while Teams queries sometimes fail.Link reference: Respond to search command

Therefore, to mitigate this behavior, you can consider trying below methods:

1) Response‑first pattern (meet the 5‑second SLA).

Always return a valid composeExtension response within ~5 seconds, the external API call with a ~4‑second safety timer. If it completes, send real results, otherwise return a lightweight default and offer an Action to continue in a dialog (task module) for long operations. This avoids “Unable to reach app” while still supporting multi‑step work.

References:

Create and send dialogs

Respond to search command

2) Eliminate cold starts and startup jitter in Azure Functions.

You can consider hosting the Node.js backend on Azure Functions Premium or Flex Consumption, enable Always‑Ready and Prewarmed instances, and add a warmup trigger to preload dependencies so the language worker is hot before Teams invokes your bot and co‑locate the Function App and any external API in the same Azure region and reuse HTTP clients with keep‑alive to avoid per‑request TLS handshakes.

References:

Azure Functions hosting options

Best practices for reliable Azure Functions

Understanding serverless cold start

Hope my answer will help you, for any further concern, kindly let me know in the comment section.

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