So here's a question I wish I'd thought to ask first: why is it that Google can return near-instantaneous search results from the entirety of the internet, but takes forever to find that recipe your Aunt Mildred emailed you two months ago? Let's let Quora user Adam D'Angelo explain:
• The total contents of the web is actually smaller than the sum of the sizes of the contents of everyone's gmail. This means it could take more servers to hold all the indexes for mail search than for web search.
• When you search the web, for the most part, you're getting the same results for your query as anyone else would get for that query. This means caching works well for web search. Most search engines have a small "hot index" with the most popular content that can handle the majority of queries which is replicated out to lots of local datacenters, giving low average response time even if the worst case is slow.
• Gmail search results are sorted by time and need to be perfect matches, whereas web search results are sorted by relevance and approximations can be made to cut corners.
Makes sense! It's not like there are popular queries that Google can put your search against to optimize results. And let's face it, three seconds may not be one second, but it's still impossibly fast—even though it may not feel that way when you're hankering for Milly's baba ganoush. [Quora via Geekosystem]