[service] [request] support parallel invocations on a single instance

One of our highly used Node.js lambdas is mostly IO-bound, waiting for a HTTP request to complete. It would be nice if a single lambda instance can handle multiple invocations in parallel, so we can save on start-up cost, have some shared cache and not run into our quota limit as fast (we're capped at 2500 at the moment, but it's not enough).

We'd use a regular Node.js service for this, but in this case we're using Lambda@edge so we're in a bind.

The specific lambda as a auth/acl check in cloudfront before we hit a S3 origin.

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**Tell us about your request**
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**Which service(s) is this request for?**
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**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
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Aucun fichier du dépôt, test ou point d’entrée n’est indiqué ; commencez par vérifier si ce dépôt de roadmap contient du code d’implémentation pour gérer les invocations de Lambda@Edge. Le travail serait considéré comme terminé lorsque la prise en charge de plusieurs invocations simultanées sur une même instance serait définie et fournie, y compris le comportement et les contraintes nécessaires au cas d’utilisation d’authentification et de CloudFront indiqué.

Rédigé par le modèle d'indexation à partir du texte de l'issue.