Azure Data Explorer succeeds because it indexes aggressively at ingest so it can ignore aggressively at query. When you "read online" in ADX, you aren't reading the data. You are reading the index of the index .
The Latency Lie: Why "Real-Time" Fails at Scale and How Azure Data Explorer Rewrites the Contract scalable data analytics with azure data explorer read online
The lie is this: "You can use your data lake for everything. Just add a little Spark, maybe a dash of Presto, and voilà—real-time analytics." Azure Data Explorer succeeds because it indexes aggressively
Your future petabyte-scale self will thank you. The Latency Lie: Why "Real-Time" Fails at Scale
If you haven't spent a weekend ingesting a billion log lines into ADX and running a summarize across them in under two seconds, you haven't yet understood what "scalable" actually means.
Most systems "read online" by brute force. They spin up 50 nodes, shuffle terabytes across the network, and pray the optimizer doesn't choke. ADX does it differently. It leverages a proprietary indexing technology that is closer to a search engine (think Elasticsearch) than a traditional database (think Postgres), but with the aggregation power of a column-store.