nlp: phonetic edit distance between a word and the closest of a set of words
Building on the comments, there's something called the Needleman–Wunsch algorithm, for which you can find the lowest 'cost' alignment of two sequences (phonemes). You can get a good 'confusion cost matrix' by taking a normal confusion matrix and taking the log-odds of each confusion pair.

As long as your set of words is less than 33k or so, you should be able to find the lowest cost match in about a second or so. Multiply that by N if you multithread across N cores...

Full disclosure: not my ideas here, I got them from Phonemic Similarity Metrics to Compare Pronunciation Methods (Hixon, Schneider and Epstein, in Interspeech 2011).