1. A computer-implemented method for creating and using a compact finite state transducer for automatic speech recognition, the method comprising: during a training period: identifying a first representation of a finite state transducer (FST) for automatic speech recognition (ASR), wherein the FST corresponds to an ASR grammar and is configured to be traversed using a first sequence of words with corresponding scores and output a second sequence of words with corresponding scores, wherein the first representation occupies a first amount of memory and comprises: a first table representing states of the FST, the first table including a first record representing a first state of the FST, the first record comprising: a 32 bit representation of a weight of the first state, and a first reference to a second record in a second table, the second record representing at least one first arc, the first arc representing a connection from the first state to another state in the FST; and the second table representing arcs of the FST, the second table including the second record representing the first arc, the second record comprising: a 32 bit representation of a weight of the first arc, a second reference to a third record in the first table, the third record representing a second state of the FST, the second state being a destination state for the first arc, a first representation of an input label of the first arc, and a second representation of an output label of the first arc; and configuring a second representation of the FST, wherein the second representation occupies a second amount of memory less than the first amount of memory and comprises: a third table representing at least a portion of the states of the FST, the third table including a fourth record representing the first state, the fourth record comprising: a 12 bit representation of the weight of the first state, and a third reference to a fifth record in a fourth table, the fifth record representing the at least one first arc; the fourth table representing at least a portion of the arcs of the FST, the fourth table including the fifth record representing the first arc, the fifth record comprising: a 12 bit representation of the weight of the first arc, a third representation of an input/output label pair corresponding to the first arc, an identifier of a destination state of the first arc, the first representation of the input label of the first arc, and the second representation of the output label of the first arc; and during a runtime period: receiving audio data comprising audio feature vectors for ASR; and determining ASR output using the second representation of the FST and the audio data.