For improved sustainability we should prefer compilation, caching, and other forms of the advance calculation of computations. The rationale for this is pretty straightforward. If there are N identical computations to be performed, and if we can perform, store, and reuse the result of one of those computations, we can reduce the total cost of computation by roughly (N-1).

Given that N can be quite large, systems that do not use these techniques can be tremendously wasteful. Interpreted programming languages stand out in this category, with perhaps the most notable example being JavaScript. The somewhat recent development of an "assembly language" for JavaScript, Web Assembly, holds some promise for a large increase in the sustainability of programs in the JavaScript ecosystem.