@Alubhate said:
ConnectionError
API key is suddenly not working, it is showing some error like
ConnectionError at /detail
HTTPSConnectionPool(host='api.themoviedb.org', port=443): Max retries exceeded with url: /3/search/movie?api_key=THE_KEY&query=Avatar (Caused by NameResolutionError(": Failed to resolve 'api.themoviedb.org' ([Errno 11001] getaddrinfo failed)"))

Maybe this will help clarify your question.

API Request Limits
First we have this information in the instructions for using the TMDb API.
https://developer.themoviedb.org/docs/rate-limiting

And Travis Bell, the Administrator, has already given us this explanation.

For API Requests:

One of our CDN providers enforces some base level rate limiting to help prevent DDOS attacks.
I believe it's a maximum of:
50 requests per second and
20 connections per IP.

See here: https://www.themoviedb.org/talk/62c7c1b258361b005fd2e747?page=1#62c83b78befd91005007a0c7

For Images:

For image.tmdb.org the only thing we limit is the max number of simultaneous connections.
The limit is the same, 20.

See here:
https://www.themoviedb.org/talk/62edd3ca46aed400917de201#62ee88e7176a940086449cdf
https://www.themoviedb.org/talk/62c7c1b258361b005fd2e747?page=1#6301a107097c49007f60374a
https://www.themoviedb.org/talk/62c7c1b258361b005fd2e747

And...
Is there really no API Rate Limiting?

The original rate limiting (40 requests every 10 seconds) has indeed been been disabled since December 2019.
There are some higher overall limits that still exists to help mitigate different attacks and the like.
I believe they sit around the 50 request per second range.

See here:
https://www.themoviedb.org/talk/6442ced4d35dea02fcfb0fab#6442d4a0d35dea0455fb1a07

I will replace your API Key with THE_KEY expression.
It is not good to show your Key to all forum users.