Will my buyers be locked out if your API is unreachable?

No, provided you build it the way the SDK does. A successful check hands back a signed token that stays valid for a grace period, so an installation that has checked in recently keeps working through a network problem on either side.

How the grace period works

When we confirm a licence, the response includes a token signed by us and valid for a window. Your item stores it and trusts it until it expires, rather than asking again every time. If we are unreachable when it next tries, the stored token carries the install through until the network comes back.

It is signed, so a buyer cannot forge one or extend it. The protection stays intact while the item stays usable.

Fail open, not closed

This is the single most important decision in your integration. Treat an unreachable API as "carry on", never as "shut down".

Consider what failing closed means in practice: our API has a bad ten minutes, and every site your buyers run goes dark at once. They do not know it was us. They know your item broke their site, and that is what the review says. A paying customer should never see your item break because of infrastructure they did not buy.

Distinguish the two cases: a definite negative, where we reply that the licence is invalid, is a real answer and you should act on it. No reply is not an answer, and should change nothing.

Practical rules

• Set a short timeout, a few seconds, so a slow response never hangs a page.
• Cache the token and check occasionally, not on every request.
• Never block installation on a check that timed out.
• Log failures for yourself, quietly, rather than showing them to the buyer.

The PHP SDK does all of this already, which is the main argument for using it.