The plural of "index"–"indexes" or "indices"?
Solution 1:
From Oxford Dictionaries:
plural of index: indexes or especially in technical use indices
The plural of index is usually spelled indexes, but can also be spelled indices (as in the original Latin) in subjects like science and medicine.
So, technically I'd use indices.
Solution 2:
Both are valid English; that is why you see both used. One person may be used to the other, while the guy down the hall says it the other way. See dictionary.com if you haven't already.