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docs/md/how_to/python/virtual_server.md

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+# Virtual Servers
+
+Perspective's Virtual Server feature lets you connect `<perspective-viewer>` to
+external data sources without loading data into Perspective's built-in engine.
+Instead, queries are translated and executed natively by the external database.
+
+For a detailed explanation of how virtual servers work, see the
+[Virtual Servers](../../explanation/virtual_servers.md) concepts page.
+
+Perspective ships with built-in virtual server implementations for:
+
+- [**DuckDB**](./virtual_server/duckdb.md) — query DuckDB databases using the
+  `duckdb` Python package.
+- [**ClickHouse**](./virtual_server/clickhouse.md) — query a ClickHouse server
+  using the `clickhouse-connect` Python package.
+- [**Polars**](./virtual_server/polars.md) — query in-memory Polars DataFrames
+  using the `polars` Python package.
+
+You can also [**implement your own**](./virtual_server/custom.md) virtual server
+to connect Perspective to any data source by subclassing `VirtualServerHandler`.