Explanation
Object Store Connector is a Mule component that allows for simple key-value storage. Although it can serve a wide variety of use cases, it is mainly design for: - Storing synchronization information, such as watermarks. - Storing temporal information such as access tokens. - Storing user information. Additionally, Mule Runtime uses Object Stores to support some of its own components, for example: - The Cache module uses an Object Store to maintain all of the cached data. - The OAuth module (and every OAuth enabled connector) uses Object Stores to store the access and refresh tokens. Object Store data is in the same region as the worker where the app is initially deployed. For example, if you deploy to the Singapore region, the object store persists in the Singapore region. MuleSoft Reference : https://docs.mulesoft.com/object-store-connector/1.1/ Data can be shared between different instances of the Mule application. This is not recommended for Inter Mule app communication. Coming to the question, object store cannot be used to share cached data if it is deployed as separate Mule applications or deployed under separate Business Groups. Hence correct answer is When there is one CloudHub deployment of the API implementation to three workers that must share the cache state.

Explanation
CloudHub object store should be in same region where the Mule application is deployed. This will give optimal performance.
Before learning about Cache scope and object store in Mule 4 we understand what is in general Caching is and other related things.
WHAT DOES "CACHING" MEAN?
Caching is the process of storing frequently used data in memory, file system or database which saves processing time and load if it would have to be accessed from original source location every time.
In computing, a cache is a high-speed data storage layer which stores a subset of data, so that future requests for that data are served up faster than is possible by accessing the data's primary storage location. Caching allows you to efficiently reuse previously retrieved or computed data.
How does Caching work?
The data in a cache is generally stored in fast access hardware such as RAM (Random-access memory) and may also be used in correlation with a software component. A cache's primary purpose is to increase data retrieval performance by reducing the need to access the underlying slower storage layer.
Caching in MULE 4
In Mule 4 caching can be achieved in mule using cache scope and/or object-store. Cache scope internally uses Object Store to store the data.
What is Object Store
Object Store lets applications store data and states across batch processes, Mule components, and applications, from within an application. If used on cloud hub, the object store is shared between applications deployed on Cluster.
Cache Scope is used in below-mentioned cases:
Need to store the whole response from the outbound processor
Data returned from the outbound processor does not change very frequently As Cache scope internally handle the cache hit and cache miss scenarios it is more readable Object Store is used in below-mentioned cases:
Need to store custom/intermediary data
To store watermarks
Sharing the data/stage across applications, schedulers, batch.
If CloudHub object store is in same region where the Mule application is deployed it will aid in fast access of data and give optimal performance.

Explanation
*Scatter Gather: When running within a transaction, Scatter Gather does not execute in parallel. This means that the second route is executed after the first one is processed, the third after the second one, etc. In case of error, all routes will be rolled back