Are there performance concerns with `return await`?

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No, there isn’t any performance problem. It’s just an unnecessary extra operation. It might take a bit longer to execute, but should be hardly noticeable. It’s akin to return x+0 instead of return x for an integer x. Or rather, exactly equivalent to the pointless .then(x => x).

It doesn’t do actual harm, but I’d consider it bad style and a sign that the author does not fully compre­hend promises and async/await.

However, there’s one case where it make an important difference:

try {
    …
    return await …;
} …

await does throw on rejections, and in any case awaits the promise resolution before catch or finally handlers are executed. A plain return would have ignored that.

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