accessing tables explicitly by index

In Oracle, is there a way to access a single row based on a specific index. Here's an example:
I have a table with a unique index made up from two columns, user_id, time_stamp. There may be thousands of rows for each user_id. I want to access the most recent row for a particular user_id without having to read thousands of rows and finding the max time_stamp. How can this be accomplished in Oracle?

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Before you buy. Received on Wed Sep 13 2000 - 17:46:17 CDT