I’ve written before about the issue of buried or implied technology in language.
But there’s another technology-related question that writers–especially writers of created-world fantasy– need to be aware of: What is the general tech level of your story?
A lot of created-world fantasy takes place in a pre-industrial setting. (Steampunk is perhaps the most obvious exception, but only if you consider steampunk to be a species of fantasy rather than a species of science fiction — a question upon which opinion is divided.) “Pre-industrial”, though, covers a lot of ground. Do you mean pre-gunpowder? Pre-clockwork? Pre-mass production and interchangeable parts? Does your society have steam engines or water wheels? Spinning wheels or drop spindles? Is your hero’s sword steel or bronze? Is his armor plate or chain or boiled leather? Does he pay the swordsmith in barter or with coin? Does his banker know about letters of credit and double-entry book-keeping? Has banking even been invented yet?
You need to think about all of these things if you’re not going to have your story taking place in an ersatz-medieval RennFaire fantasyland — and you need to make certain that your tech levels match across the board.
(Yes. This means that you have to do research if you’re going to write fantasy. Books like The Timelines of History and television programs like the old BBC Connections series are a good place to start.)