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Dynamic mapping is convenient right up until it isnt. Field explosion, ILM policies, shard sizing, and the index template that keeps an Elasticsearch cluster from mapping itself into a corner.
ELK is four separate tools that happen to ship together. What Elasticsearch, Logstash, Beats, and Kibana each actually do, how they fit into a pipeline, and when the stack is worth the operational weight.
Monitoring tells you WHEN something broke. Observability tells you WHY. A practical guide to structured logging, correlation IDs, intentional log levels, and connecting logs to traces.