You can form a partition key by concatenating multiple property values into a single artificial partitionKey property. These keys are referred to as synthetic keys.
Another possible strategy to distribute the workload more evenly is to append a random number at the end of the partition key value. When you distribute items in this way, you can perform parallel write operations across partitions.
Note: It's the best practice to have a partition key with many distinct values, such as hundreds or thousands. The goal is to distribute your data and workload evenly across the items associated with these partition key values. If such a property doesn't exist in your data, you can construct a synthetic partition key.
References:
https://docs.microsoft.com/en-us/azure/cosmos-db/synthetic-partition-keys

Explanation

Box 1: SAS tokens
Custom topics use either Shared Access Signature (SAS) or key authentication. Microsoft recommends SAS, but key authentication provides simple programming, and is compatible with many existing webhook publishers.
In this case we need the expiration time provided by SAS tokens.
Box 2: ValidationCode handshake
Event Grid supports two ways of validating the subscription: ValidationCode handshake (programmatic) and ValidationURL handshake (manual).
If you control the source code for your endpoint, this method is recommended.

Explanation

Scenario: Exclude non-user actions from Application Insights telemetry.
Box 1: ITelemetryProcessor
To create a filter, implement ITelemetryProcessor. This technique gives you more direct control over what is included or excluded from the telemetry stream.
Box 2: ITelemetryProcessor
Box 3: ITelemetryProcessor
Box 4: RequestTelemetry
Box 5: /health
To filter out an item, just terminate the chain.
Reference:
https://docs.microsoft.com/en-us/azure/azure-monitor/app/api-filtering-sampling

Reference:
https://docs.microsoft.com/en-us/azure/app-service/manage-scale-per-app

References:
https://azure.microsoft.com/es-es/blog/offline-sync-for-mobile-services/