[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**
What do you want us to build?

**Which service(s) is this request for?**
This could be AWS Lambda itself, or integrations with other services.

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
What outcome are you trying to achieve, ultimately, and why is it hard/impossible to do right now? What is the impact of not having this problem solved? The more details you can provide, the better we'll be able to understand and solve the problem.

**Are you currently working around this issue?**
How are you currently solving this problem?

**Additional context**
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Es werden keine Repository-Dateien, Tests oder Einstiegspunkte genannt; beginne damit zu prüfen, ob dieses Roadmap-Repository Implementierungscode für die Verarbeitung von Lambda@Edge-Aufrufen enthält. Erledigt wäre die Definition und Bereitstellung der Unterstützung für mehrere gleichzeitige Aufrufe auf einer Instanz, einschließlich des für den genannten Authentifizierungs- und CloudFront-Anwendungsfall erforderlichen Verhaltens und der erforderlichen Einschränkungen.

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