Question about "Unknown" Host in Performance Insights - Support ID 07C8914A72D23542BFA2286BF5260D75F6FAF477

In Performance Insights, when you see "Unknown" host in the Top hosts section, this typically refers to database activity that Performance Insights cannot attribute to a specific host or client connection.

Based on similar cases, the "Unknown" host designation often represents internal database processes or system activities rather than an actual external client connection. For PostgreSQL RDS (which appears to be what you're using based on your question), this could be related to Performance Insights collecting data from the database engine's internal tables.

In Oracle databases, for example, Performance Insights shows SQL text as "Unknown" in specific situations such as when a database user other than SYS is active but not currently executing SQL, or when background processes are performing certain operations.

The Support ID you've provided (07C8914A72D23542BFA2286BF5260D75F6FAF477) is specific to your instance and can be referenced if you need to contact AWS Support for more detailed investigation of this particular case.

If you're troubleshooting performance issues and need to identify actual client connections causing load, focus on the connections that have identifiable hosts rather than the "Unknown" entries.
Sources
What is Unknown host under Top hosts on PostgreSQL RDS | AWS re:Post
Analyzing queries with the Top SQL tab in Performance Insights - Amazon Relational Database Service
Amazon RDS Performance Insights | Cloud Relational Database | Amazon Web Services

In Amazon RDS Performance Insights, when you see "Unknown" as a host, it generally means that the information is unavailable or unlabelled from the database engine's internal tables. Performance Insights gathers its data from these internal tables, and if a field like the host name is NULL or empty, it will be displayed as "Unknown" to accurately represent the data. This isn't necessarily a system user or an internal process, but rather a catch-all for connections where the host information couldn't be collected or was not provided by the client connecting to the database. It is a common occurrence and often doesn't indicate a critical problem, but it can make it difficult to trace the source of a high database load. To investigate further, you may need to use other tools, such as the database's own log files or by running queries directly on the database to get active session details.

You can learn more about diagnosing and resolving performance issues with Amazon RDS in a video from re:Invent. re:Invent 2023 - Take a load off: Diagnose & resolve performance issues with Amazon RDS