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We combine them:

Kibana + Elasticsearch

Grafana + Elasticsearch / Prometheus / some other sources

Prometheus is good for handling the VERY massive number of events. Because it stores aggregated metrics.

Elasticsearch is good for more detailed data exploration. Because it stores each event as a single document with all info you want. For example, in elasticsearch, you may store all logs from your app, visualize some metrics based on these logs, and also be able to view each log message with all extra fields separately, write insane queries, and so on.

Grafana is good for drawing metrics from many sources(e.g. Prometheus, Elasticsearch, MySQL, etc).

Kibana is good as a UI for Elasticsearch. It is able to do things that Grafana can't

We have to use it. Our company uses Skype as an organization-wide messenger from time immemorial. Many do not really like it, but it's free, and many of our clients/partners have it too, and also it's just a matter of habit.

Though many teams use different messengers for inter-team communications. e.g Slack or Discord.