title: Azure Data Explorer (ADX) vs Polybase vs Databricks
body: <h2>Question</h2>
  
  <p>Today I discovered another Azure service called <a href="https://docs.microsoft.com/en-us/azure/data-explorer/data-explorer-overview" rel="noreferrer">Azure Data Explorer (ADX)</a>. Sorry for such comparison of services, I have good understanding of all except ADX. I feel like there is a big functionality overlay, so want to know the exact role of ADX in Azure infrastructure.</p>
  
  <p><em>What is the use case when ADX is significantly better than Synapse/Databricks?</em></p>
  
  <h2>My understanding of ADX</h2>
  
  <p>AFAIK, ADX is a cluster (with per hour billing, like Databricks or Synapse, not like ADLA) that is handling database for you and is optimized for streaming ingestion and ad-hoc queries at scale. It also supports external tables, that has worse performance but cheaper (you pay for Blob/ADLS storage).</p>
  
  <h2>Details</h2>
  
  <p>I don't understand why do we need ADX if:</p>
  
  <ol>
  <li>Azure Synapse has similar pricing model (cluster, per-hour), also it supports streaming ingestion and ad-hoc querying at scale. Azure Synapse support querying BlobStorage/ADLS through Polybase external tables.</li>
  <li>Databricks is another service that is capable of doing it. Using Databricks Ingest and Delta Lake - you can ingest streaming data and consume them in both: streaming and batching way. Actually you can have interactive cluster that will handle ad-hoc queries for you.</li>
  <li>Also if you want a real-time analytics - use Azure Stream Analytics. If you want Athena-like experience - use ADLA (still it doesn't support ADLS gen2).</li>
  </ol>