Rate limits on metadata server access token requests

[kevinAlbs]

Hello,

I want to get the access token for an attached service account without using a Google auth library.

Referring to AIP-4115, I am able to obtain an access token by making a request to the metadata server:

curl -H "Metadata-Flavor: Google" http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/token

Output resembles the following:

{ "access_token": "...", "expires_in": 3599, "token_type": "Bearer" }

My question is: Is there a rate limit for these requests?

Other relevant background and research:

• This only needs to work on GCE Equivalent Runtimes
• GCE documentation says the metadata server caches tokens, so this may suggest there is no rate limit:

Access tokens expire after a short period of time. The metadata server caches access tokens until they have 5 minutes of remaining time before they expire. You can request new tokens as frequently as you like, but your applications must have a valid access token for their API calls to succeed.

• https://stackoverflow.com/questions/58495465/what-is-the-rate-limit-for-gce-instance-metadata-servic... asks a similar question but is unanswered.
• I attempted to make repeated requests in a loop to the metadata server, but did not receive any error.

Thank you.