As a developer tools analyst, I've compared OpenTSDB and Thanos, two open-source projects catering to distinct time series database needs, for senior engineers. Here's a factual overview of their momentum, community size, and apparent use cases: **Momentum and Community Size**: Thanos (thanos-io/thanos) exhibits significantly higher momentum, with 13,992 stars and a notable 57 stars gained in the last 30 days, indicating strong recent interest. In contrast, OpenTSDB (opentsdb) has 5,064 stars with only 3 added in the last 30 days, suggesting a more stable but less dynamically growing community at present. **Apparent Use Cases**: OpenTSDB is positioned as a general-purpose, scalable, distributed Time Series Database, suitable for a broad range of applications requiring high throughput and storage of time-stamped data. Thanos, as a CNCF Incubating project, is specifically designed for highly available Prometheus setups, focusing on long-term storage capabilities. This aligns Thanos closely with Prometheus users seeking scalable, durable metric storage solutions. Both projects serve the time series data space but cater to different primary use cases: OpenTSDB for general time series database needs and Thanos for enhancing Prometheus deployments. Engineers should choose based on whether their needs are more aligned with general time series storage (OpenTSDB) or integrated Prometheus scalability (Thanos).