A feature that is in tech preview might have limited to no documentation, no support, and is not guaranteed to be made available as GA in the future. Some products or projects may also call this stage alpha.
A tech preview feature or version should not be depended upon in a production environment.
Tech preview features are experimental. Interfaces for features in tech preview could change in backwards-incompatible ways. Do not count on the feature becoming a formal product, and expect it to change heavily if it does.