Defer Await Until Needed
Move await operations into the branches where they're actually used to avoid blocking code paths that don't need them.
Incorrect (blocks both branches):
async function handleRequest(userId: string, skipProcessing: boolean) {
const userData = await fetchUserData(userId);
if (skipProcessing) {
// Returns immediately but still waited for userData
return { skipped: true };
}
// Only this branch uses userData
return processUserData(userData);
}Correct (only blocks when needed):
async function handleRequest(userId: string, skipProcessing: boolean) {
if (skipProcessing) {
// Returns immediately without waiting
return { skipped: true };
}
// Fetch only when needed
const userData = await fetchUserData(userId);
return processUserData(userData);
}Another example (early return optimization):
// Incorrect: always fetches permissions
async function updateResource(resourceId: string, userId: string) {
const permissions = await fetchPermissions(userId);
const resource = await getResource(resourceId);
if (!resource) {
return { error: "Not found" };
}
if (!permissions.canEdit) {
return { error: "Forbidden" };
}
return await updateResourceData(resource, permissions);
}
// Correct: fetches only when needed
async function updateResource(resourceId: string, userId: string) {
const resource = await getResource(resourceId);
if (!resource) {
return { error: "Not found" };
}
const permissions = await fetchPermissions(userId);
if (!permissions.canEdit) {
return { error: "Forbidden" };
}
return await updateResourceData(resource, permissions);
}This optimization is especially valuable when the skipped branch is frequently taken, or when the deferred operation is expensive.