Build Alert Dashboard from Cloudwatch streamed log

Hi community, I am currently developing some dashboards and I am struggling with one requirement that is building an alert list triggered by ERROR or WARN messages from a streamed log to cloudwatch (this file is ingested from an EC2 instance).

I could build the dashboard with the default dimensions but I need the solution to consider the custom ingested log. I saw one response in the community that recommended to use ElasticSearch service but I prefer not to take that path for now.

Any sugestions?

Thanks in advance.