Splunk
Logs and SIEM platform — Michael Baum, Rob Das, Erik Swan, 2003. Acquired by Cisco in 2024 for 28 BUSD. Standard in Fortune 500 security and operations teams.
Custom query language (SPL — Search Processing Language) over schema-on-read data. Apps + add-ons for 2000+ data sources. Splunk Enterprise Security is its flagship SIEM. Splunk Observability (ex-SignalFx) for APM/metrics.
Famous for being expensive — license billing per indexed GB was long the biggest complaint. Competitors: Elastic SIEM, Sentinel (Azure), Sumo Logic, Datadog. Splunk lives on enterprise security, regulatory compliance and unshakeable lock-ins.