```sh
# Get the IDs of running nginx instances in 'dev'.
aws ec2 describe-instances --output 'text' \
  --filters \
    'Name=instance-state-name,Values=running' \
    'Name=tag:env,Values=dev' \
    'Name=tag:app,Values=nginx' \
  --query 'Reservations[].Instances[].InstanceId[]'
```

https://instances.vantage.sh/
https://ec2instances.github.io/