I really have no idea what is wrong with Spotify’s API, but the HTTP 429 errors suddenly kicked in again at around 2025-07-07T01:05:00Z:
Spotify rate limit error (HTTP 429): Retry-After 30827
With the retry-after value being in seconds, this would mean that Harmony has to wait more than 8 hours(!) until the next API request.
Since this is an unreasonable delay (and I’ve luckily implemented an upper limit), I’m simply letting these requests fail.
Unfortunately this doesn’t seem to be a unit mistake or something similar, because the errors continued for the next 7 hours with the value slightly decreasing. Apparently the API will start working again in about 80 minutes 
What is confusing is that the API went straight from answering every request to straight out blocking Harmony for many hours, apparently without a chance to avoid that.
(The Spotify API documentation only talks about a 30 second window and the Retry-After header without ever mentioning a concrete rate limit for this window, so that doesn’t help either.)
P.S. We are not alone with this issue but Spotify support doesn’t seem to care?