On scalability and memory footprint
ericb: If you're building a fairly standard web app you probably shouldn't be worrying at this stage. Keeping memory usage low does not mean a significant speedup necessarily. It means your memory usage will be low. Sometimes you trade one thing for another depending on what you're doing.When the app is written, if you run a load test (or you can let your users be your load test, like Twitter), there will be a bottleneck for some n of users. Remove this bottleneck, which could be cpu, database, memory, connections, bandwidth, etc., and there will be a new bottleneck at some > n users.  Rinse, lather, repeat.If you optimize now, you're most certainly optimizing the wrong thing. When I load tested my first production rails app, I found cpu was the first bottleneck I hit, not memory.