Which AWS service will meet this requirement?

Explanations:

Amazon Neptune is a graph database service designed for storing and navigating relationships between data. It is not optimized for time-series data and does not scale for the analysis of trillions of events each day.

Amazon Timestream is a purpose-built time-series database service designed specifically for storing and analyzing time-series data efficiently. It can handle trillions of events per day and allows for quick queries and analytics, making it ideal for the stated requirements.

Amazon Forecast is a machine learning service that provides forecasting capabilities based on historical time-series data. While it deals with time-series data, it is not a database service for storing and analyzing large volumes of events.

Amazon DocumentDB is a document database service compatible with MongoDB. It is not designed for time-series data specifically and is more suited for storing semi-structured data rather than efficiently processing trillions of events daily.