> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-detect-table-modification.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

> Overview page of Performance and Optimizations

# Performance and Optimizations

This section contains tips and best practices for improving performance with ClickHouse.
We recommend users read [Core Concepts](/concepts/core-concepts/parts) as a precursor to this section,
which covers the main concepts required to improve performance.

<CardGroup cols={2}>
  <Card title="PREWHERE optimization" icon="filter" href="/concepts/features/performance/prewhere">
    How `PREWHERE` reduces I/O by filtering data before reading unnecessary columns, and how to monitor its effectiveness.
  </Card>

  <Card title="Allocation profiling" icon="memory" href="/concepts/features/performance/allocation-profiling">
    Profile memory allocations with jemalloc.
  </Card>

  <Card title="Allocation profiling for versions before 25.9" icon="clock-rotate-left" href="/concepts/features/performance/allocation-profiling-old">
    Allocation profiling for ClickHouse versions before 25.9.
  </Card>

  <Card title="Caches" icon="hard-drive" href="/concepts/features/performance/caches/caches">
    Cache types, including the query cache, query condition cache, and userspace page cache.
  </Card>

  <Card title="Data skipping indexes" icon="forward" href="/concepts/features/performance/skip-indexes/skipping-indexes">
    Understanding data skipping indexes, with examples.
  </Card>

  <Card title="Lazy materialization" icon="hourglass-half" href="/concepts/features/performance/lazy-materialization">
    Defer reading column data until it is actually needed.
  </Card>

  <Card title="Troubleshooting" icon="bug" href="/concepts/features/performance/troubleshoot/debugging-memory-issues">
    Debugging memory issues, testing your hardware, and the sampling query profiler.
  </Card>
</CardGroup>