REST and CSOM much slower than List Web Service

Question

lists.asmx = Web Service
listdata.svc = REST API
client.svc = CSOM

Using JavaScript to query a list using the 3 available APIs, I'm finding lists.asmx responds much faster than listdata.svc or client.svc. For all three queries, I'm setting the ViewFields and/or $select properties to pull only 3 fields from the list which has about 400 items

I see this trend on my local SP2010 VM, and the SP2010 servers my company has deployed.

API            Size     Timeline
lists.asmx     46KB     131ms
listdata.svc   12.5KB   889ms
client.svc     40KB     326ms

What's going on? Why would these two new (to 2010) APIs be slower?

Answer 1

Try to limit your query: Use the ViewFieldsOnly flag. Be sure that it is set! You can use the CAML query builder to check your queries: http://www.codeproject.com/Articles/458008/CAML-Query-Builder

Answer 2

Alway use filters for indexed columns first, like

Query = "<Where><Geq><FieldRef Name='ID' /><Value Type='Number'>1</Value></Geq</Where>"

that will increase performance. So query with indexed field ID faster then without.