An ecommerce company uses a set of AWS Lambda functions to process orders.

The correct answer is C because the requirement is for a live feed of log events in near real time , filtered to show only lines that begin with “ERROR.” The live tail feature for AWS Lambda and CloudWatch Logs is specifically intended for this kind of operational debugging. It allows developers to watch logs as they are generated and apply filtering so they can focus only on relevant messages during active troubleshooting.

This is particularly suitable because the function is already in production , and the company wants immediate visibility into timeout-related issues without waiting for a full batch of logs to accumulate. With live tail and a filter expression for ERROR , the developer can observe only the important log lines as new invocations happen, which speeds up root-cause analysis.

Option A is not the best answer because CloudWatch Logs Insights is powerful for querying logs, but it is primarily used for searching and analyzing logs after they have been collected, not as a continuous near-real-time live stream. Option B is incorrect because a subscription filter is used to forward logs to another destination such as Lambda, Kinesis, or Firehose; it is not the simplest way to give an operator a live interactive filtered view. A metric filter also creates metrics from log patterns but does not present the actual live log lines for review. Option D is incorrect because Amazon Athena is not used directly for querying CloudWatch Logs in real-time operational troubleshooting.

Therefore, the best solution is to use live tail with an ERROR filter to inspect relevant Lambda log events as they occur.