---
title: InfluxDB internals
description: Learn about internal systems and implementation details of InfluxDB Clustered.
url: https://docs.influxdata.com/influxdb3/clustered/reference/internals/
estimated_tokens: 480
product: InfluxDB Clustered
version: clustered
---

# InfluxDB internals

### [Arrow Flight SQL](/influxdb3/clustered/reference/internals/arrow-flightsql/)

The InfluxDB SQL implementation uses **Arrow Flight SQL** to query InfluxDB and return results.

### [InfluxDB Clustered data durability](/influxdb3/clustered/reference/internals/durability/)

Data written to InfluxDB Clustered progresses through multiple stages to ensure durability, optimized performance and storage, and efficient querying. Configuration options at each stage affect system behavior, balancing reliability and resource usage.

### [Data retention in InfluxDB Clustered](/influxdb3/clustered/reference/internals/data-retention/)

InfluxDB Clustered enforces database retention periods at query time and, to optimize storage, routinely deletes [Parquet](https://parquet.apache.org/) files containing only expired data.

### [InfluxDB 3 storage engine architecture](/influxdb3/clustered/reference/internals/storage-engine/)

The InfluxDB 3 storage engine is a real-time, columnar database optimized for time series data that supports infinite tag cardinality, real-time queries, and is optimized to reduce storage cost.

### [Query plans](/influxdb3/clustered/reference/internals/query-plan/)

A query plan is a sequence of steps that the InfluxDB Querier devises and executes to calculate the result of a query in the least amount of time. InfluxDB query plans include DataFusion and InfluxDB logical plan and execution plan nodes for scanning, deduplicating, filtering, merging, and sorting data.