Time and relative limits in space

We readily admit that this section header is a stretch (if you're not familiar with it, try searching for TARDIS on the Web), but there are only so many phrases related to time travel that can be replaced with the word limit. One of the amazing features of Apex is that it allows you to program back in time. Despite the fact that Apex and the Salesforce1 Platform are updated three times a year, Apex is fully backward compatible. In fact, you can write your code today under the current Apex limits, and then with a few keystrokes magically send your code back in time to a previous API version with historical limits.

Part of every Apex class is a bit of metadata that defines under which API version the code should run. This value stays set unless you modify it. That means that if your code behaves correctly today, it should continue to behave the exact same, even as the Salesforce1 Platform continues to be updated over time. This metadata is accessible in both...