Lambda Advanced Logging Controls Prerequisite

The correct answer is C. The question specifies that the Lambda function uses managed runtimes, which support Advanced Logging Controls. This feature allows developers to configure separate log levels for application logs and system logs directly within the Lambda console or via AWS CLI, without modifying the function code.

However, Advanced Logging Controls has a strict prerequisite: the Lambda function must be configured to use the JSON log format. If the function is using the default text-based log format, the advanced logging controls settings (such as setting app logs to ERROR and system logs to WARN) will not take effect. Therefore, the necessary step to meet the requirement is to switch the log format to JSON.

Let's evaluate the other options:

• Option A is incorrect because permissions do not control log verbosity or format. The function already successfully writes logs, indicating sufficient permissions.
• Option B is incorrect because setting the log level in the code affects only application-specific logging statements (e.g., console.error). It does not control the verbose system logs generated by the Lambda runtime (e.g., cold starts, initialization errors), which require the Advanced Logging Controls feature. Furthermore, changing code contradicts the typical efficiency goals of serverless configurations where possible.
• Option D is incorrect because sending logs to a custom log group does not change the filtering level of the messages contained within those logs.

This topic covers Data Operations and Support, specifically how to manage and monitor data pipelines by optimizing observability. Getting this wrong leads to excessive log storage costs and noise in CloudWatch Insights, making it harder to identify actual errors in data processing pipelines.