HubSpot recently changed there authentication mechanism now we have to use access token instead of API key. So my question is can we use the Legacy Contacts APIs with the new authentication mechanism for a long time or they can completely discontinue the legacy apis?
I think HubSpot lines out the legacy API stipulations here pretty clearly. Some legacy APIs haven't been updated. Some have and you are encouraged to use the new. Some are depreciated and should not be used in new development and should be updated to newer versions. Pretty standard with APIs. As new versions are created, eventually old versions will be depreciated.
That being said, the movement away from API keys to private apps/OAuth is really a totally different topic. The different authentication mechanisims can be used with new and old versions of the API.
