Monitoring is still as important as it already was, if not more.
As there is no "one size fits all", each project has to decide what (monitoring-) solution or technology fits best. For cloud - centric solutons and deployments (think Azure, AWS, ... projects), just look for monitoring services etc. on the platform your project is being deployed to. Using anything "platform-native" should be the most efficient choice and get the best price-performance ratio.
Still there are some "names" coming up more often than others:
NewRelic: Monitoring infrastructure, application and usage metrics.
App Insights: Know what happens in / with your application(s)
Prometheus: An open source solution for timeseries data like metrics with a whole bunch of solutions for querying, alerting and visualization.
After development, any application/service is stripped of debugging functionality and instrumentation.
The only chance to keep an eye on success/failure is to observe the system(s) for
... is observing the application/service, its runtime environment and infrastructure "from the outside" in (almost) real time.
Possible results are:
Monitoring data is being used to control and manage the application/service "in time". It helps to get "the right fit" of the infrastructure (scaling) or enables runtime management according to SLAs.
... is any kind of usage information about the application/service and its runtime environment.
Telemetric data is somewhat similar to Monitoring data, but is meant to be used "somewhere else" and mostly for statistical purposes. It is especially required for improvement of software/services based on usage info.
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