The Stacks project

Lemma 21.47.2. Let $(\mathcal{C}, \mathcal{O})$ be a ringed site. Let $E$ be an object of $D(\mathcal{O})$.

1. If $\mathcal{C}$ has a final object $X$ and there exist a covering $\{ U_ i \to X\}$, strictly perfect complexes $\mathcal{E}_ i^\bullet$ of $\mathcal{O}_{U_ i}$-modules, and isomorphisms $\alpha _ i : \mathcal{E}_ i^\bullet \to E|_{U_ i}$ in $D(\mathcal{O}_{U_ i})$, then $E$ is perfect.

2. If $E$ is perfect, then any complex representing $E$ is perfect.