In a blog post, Goutham Veeramachaneni discusses improvements to backfill methods for importing older data into Prometheus, focusing on two main approaches: retroactive rule persistence and bulk data import from CSV files. Retroactive rule persistence aims to address issues with recording rules in Prometheus, where new recorded metrics only exist from the time a recording rule is added, causing delays in dashboard updates. A community bridge mentee has proposed a design to add a backfill command to promtool, allowing users to specify recording rules and time ranges for backfilling. The bulk import approach involves supporting CSV and OpenMetrics formats for importing data, which could be useful for analyzing data with PromQL or migrating from other systems. A proof of concept for CSV-based import has been developed, but improvements are needed, such as simplifying the CSV format and implementing data batching. Additionally, the post mentions the potential for an online backfill method that would allow streaming data into Prometheus, with plans to refine this based on user feedback and experiences with the offline tools.