An observability platform is an end-to-end system that helps organizations understand the health of their applications and services. This understanding comes from the three pillars of modern observability: metrics (time series data), logs (text-based data), and traces (request data with associated baggage/metadata).
Nice overview of modern observability systems! I'd mention also VictoriaMetrics, which is frequently used as a building block for large-scale monitoring systems, since it needs less CPU, RAM and storage space than competing solutions. It is also much easier to setup and operate.
There is also VictoriaLogs - user-friendly open source database for logs. Comparing to Elasticsearch, it needs 30x less RAM and 15x less disk space.
Nice overview, Kevin. Very informative.