In the context of ORMs, which statement best contrasts eager loading and lazy loading?

• A. Eager loading fetches data upfront; Lazy loading fetches data on demand.
• B. Eager loading fetches data after the first query; Lazy loading caches results.
• C. Eager loading uses less memory than lazy loading.
• D. Both loading strategies always have the same performance characteristics.

Answer: (A)

In ORMs, the timing of loading related data is what sets eager loading apart from lazy loading. Eager loading fetches the related data upfront as part of the initial query, so you have everything you need in one go and avoid additional database trips when you access those relationships. Lazy loading, on the other hand, waits until you actually access the related property, at which point it issues separate queries to fetch that data, which can lead to many small round-trips if you loop over items with relationships.

That contrast—data being fetched upfront versus on demand—is what makes the statement correct. The idea that eager loading happens after the first query, or that lazy loading caches results, isn’t accurate by definition. Also, memory usage and performance aren’t fixed rules: eager loading can use more memory by loading extra data, while lazy loading can incur more queries and potential latency if you access many relationships. And the two strategies do not always share the same performance characteristics.