Google search appliance
GSA (Google) is targted to companies that want a simple experiance for indexing their web and database hosted content. It is possible to index other systems as long as the data can be exposed in the form of a Google feed. So once the data is in a format that Google understands, it applies the Google technology to determine how best to index that document.
Google Search Appliance works great. It can search in meta-data, get selective data back from query, see real time status of documents that are getting crawled, scalable with GSA6.14 and all great support from Google.
FAST is at the other end of the spectrum. It works with all the same types of data sources (structured – DBA and unstructured – Web/Documents). However FAST allows you to have fine grained control on how the data is processed and inserted into the Index.
FAST does not provide a trial download of their Enteprise Search Platform (ESP) today nor it’s SDK.FAST is pretty much the industry leader for customization which is what you are likely intrested in an API for.
So if you need to control the indexing process FAST is your friend. It allows you to define fields, map properties into these fields and then gives you a powerful query API (via HTTP) to search that content.
FAST also provides an extremely scalable product because of the way it divides the index up. Google does not provide this level of control because it is a “black box”.
The Query API is very similar between Google and FAST. They both use HTTP to craft the query and return the result.
Our advice if you are happy with the Google experience then stay with it. If you are not happy and really want to control the processing workflow or need to scale up then go with FAST.