CartoDB-SQL-API/doc/query_optimizations.md

Query Optimizations

There are some tricks to consider when using the SQL API that might make your application a little faster.

• Only request the fields you need. Selecting all columns will return a full version of your geometry in the_geom, as well as a reprojected version in the_geom_webmercator.
• Use PostGIS functions to simplify and filter out unneeded geometries when possible. One very handy function is, ST_Simplify.
• Remember to build indexes that will speed up some of your more common queries. For details, see Creating Indexes
• Use cartodb_id to retrieve specific rows of your data, this is the unique key column added to every CARTO table. For a sample use case, view the Faster data updates with Carto blogpost.