> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-mintlify-3a82795f.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Performance and optimizations

> Overview of performance and optimization features in ClickHouse

This section covers features and techniques for improving query and ingestion
performance with ClickHouse. We recommend reading
[Core Concepts](/concepts/core-concepts/parts) first for the foundational
material these guides build on.

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

  <Card title="Allocation profiling" icon="chart-line" href="/concepts/features/performance/allocation-profiling">
    Profile memory allocations to diagnose memory pressure and tune resource usage in ClickHouse.
  </Card>

  <Card title="Caches" icon="bolt" href="/concepts/features/performance/caches/caches">
    Query cache, query-condition cache, and userspace page cache for accelerating repeated workloads.
  </Card>

  <Card title="Skip indexes" icon="forward" href="/concepts/features/performance/skip-indexes/skipping-indexes">
    Use secondary skip indexes to prune irrelevant data blocks and accelerate filtered queries.
  </Card>

  <Card title="Lazy materialization" icon="clock" href="/concepts/features/performance/lazy-materialization">
    Defer column reads until they are needed to reduce I/O for selective queries.
  </Card>

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