postgres single rows vs array
Regardless of EC2,


do what makes sense for the data
don't pre-optimize


Columns are not for similar-data that serve the same purpose. If you're writing entries use rows. If you're describing them use columns. Let aggregates do the voodoo of taking the data from the rows and rolling it up to something useful.

Now for your application, if I was doing GPS stuff, I would not be using separate columns for lat and long but instead I would use


PostGIS and the GEOGRAPHY type,
or, if not possible, the point(long, lat) (at least it supports &lt;@&gt; (distance)) as well as some other useful operators and you can upgrade later