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Resource filtering is designed primarily for textual resources in which Maven substitutes property expressions. Binary files such as PKCS#12 keystores and certificate files must not be passed through text filtering because filtering can corrupt their binary representation.

The Maven Resources Plugin provides the dedicated configuration element nonFilteredFileExtensions. Each additional extension is declared using a nested nonFilteredFileExtension. The plugin documentation specifically defines this parameter as the list of additional file extensions to which filtering must not be applied.

Option C correctly uses the documented structure:

< nonFilteredFileExtensions >

< nonFilteredFileExtension > p12 < /nonFilteredFileExtension >

< nonFilteredFileExtension > crt < /nonFilteredFileExtension >

< nonFilteredFileExtension > pem < /nonFilteredFileExtension >

< /nonFilteredFileExtensions >

This is important because the application's normal resource configuration can still use < filtering > true < /filtering > for textual files while Maven leaves the listed certificate/keystore formats untouched.

The alternative constructs visible in the other exhibits, such as excludeFileExtensions or excludeBinaryFiles, are not the Maven Resources Plugin parameter used for this purpose.

Reference topics: Maven Resources Plugin; resource filtering; binary resources; nonFilteredFileExtensions; Mule Maven builds.

Official documentation: https://maven.apache.org/plugins/maven-resources-plugin/resources-mojo.html

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The relevant property is the HTTP semantics of PUT. PUT is designed to be idempotent: repeating the same request against the same resource should establish the same intended resource state rather than repeatedly creating additional side effects. This characteristic makes PUT appropriate when an Until Successful scope might retransmit an operation following a transient failure.

For example, the downstream system might process the initial PUT successfully but the Mule application might experience a network error before receiving the response. Until Successful could therefore invoke the same PUT again. Provided the upstream APIs correctly implement standard PUT semantics, repeating the same modification produces the intended final state rather than duplicating the operation.

Changing PUT to POST would generally make the design less suitable because POST is not inherently idempotent. Executing the operations sequentially changes concurrency but does not itself establish idempotency. Compensating transactions address distributed rollback and consistency when independent operations partially succeed; they are a different reliability concern from idempotent retry behavior.

MuleSoft documents Until Successful as retrying the contained processors until they succeed or retries are exhausted.

Therefore, under the REST/HTTP semantics assumed by the question, no additional Mule processing is required.

Reference topics: Until Successful; idempotent operations; HTTP PUT semantics; reliable retries; Scatter-Gather.

Official documentation: https://docs.mulesoft.com/mule-runtime/latest/until-successful-scope

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The distinction between entry TTL and expiration interval is the key to this question. entryTtl="1" specifies that an Object Store entry becomes eligible for expiration after one second. However, expirationInterval="30" determines how frequently Mule's expiration process checks the Object Store and removes expired entries.

MuleSoft describes the expiration interval as the frequency at which the expiration thread runs. Therefore, expiration is not equivalent to immediate physical removal at precisely the TTL boundary.

The flow first sets the payload to originalPayload, then stores "testPayload" under the key testKey. Ten seconds subsequently elapse before the Retrieve operation executes. Although this exceeds the configured one-second TTL, only 10 seconds have elapsed since storage, while the expiration process is configured to run at 30-second intervals. The entry has therefore not yet been evicted when retrieval occurs.

Because testKey remains available, os:retrieve returns the stored value, testPayload. The configured default value nullPayload would be used only if the key were unavailable according to the Retrieve operation's behavior.

Reference topics: Object Store Connector; entry TTL; expiration interval; expiration thread; Store and Retrieve operations.

Official documentation: https://docs.mulesoft.com/object-store-connector/latest/object-store-connector-reference

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