Net::Google::SafeBrowsing2 implements the Google Safe Browsing
v2 API.

The library passes most of the unit tests listed in the API
documentation. See the documentation
(http://code.google.com/apis/safebrowsing/developers_guide_v2.html)
for more details about the failed tests.

The Google Safe Browsing database must be stored and managed locally.
Net::Google::SafeBrowsing2::Sqlite uses Sqlite as the storage back-end,
Net::Google::SafeBrowsing2::MySQL uses MySQL. Other storage mechanisms
(databases, memory, etc.) can be added and used transparently with this module.

You may want to look at "Google Safe Browsing v2: Implementation Notes"
(http://www.zscaler.com/research/Google%20Safe%20Browsing%20v2%20API.pdf),
a collection of notes and real-world numbers about the API. This is intended
for people who want to learn more about the API, whether as a user or to
make their own implementation.