draw.io

Teamwork flow: https://app.diagrams.net/#Hairdb/drawio/main/team/airdb-teamwork-flow.drawio

https://app.diagrams.net/#Hairdb/drawio/main/network/cause-of-network-failure.drawio

https://app.diagrams.net/#Hairdb/drawio/main/program-unstanding.drawio

Examples:

https://info.seibert-media.net/display/DRAWIO/draw.io+for+Confluence+-+Example+Diagrams

drawio-libs: http://jgraph.github.io/drawio-libs/

PlantUML

Refer:

https://github.com/joelparkerhenderson/plantuml-examples