---
title: "Which Latency Numbers Should You Know?"
description: "Essential latency benchmarks for developers and system designers."
image: "https://assets.bytebytego.com/diagrams/0250-latency-numbers.jpg"
createdAt: "2024-03-11"
draft: false
categories:
  - caching-performance
tags:
  - "latency"
  - "performance"
---

Please note those are not accurate numbers. They are based on some online benchmarks (Jeff Dean’s latency numbers + some other sources).

![](https://assets.bytebytego.com/diagrams/0250-latency-numbers.jpg)

*   **L1 and L2 caches: 1 ns, 10 ns**

    E.g.: They are usually built onto the microprocessor chip. Unless you work with hardware directly, you probably don’t need to worry about them.

*   **RAM access: 100 ns**

    E.g.: It takes around 100 ns to read data from memory. Redis is an in-memory data store, so it takes about 100 ns to read data from Redis.

*   **Send 1K bytes over 1 Gbps network: 10 us**

    E.g.: It takes around 10 us to send 1KB of data from Memcached through the network.

*   **Read from SSD: 100 us**

    E.g.: RocksDB is a disk-based K/V store, so the read latency is around 100 us on SSD.

*   **Database insert operation: 1 ms**

    E.g.: Postgresql commit might take 1ms. The database needs to store the data, create the index, and flush logs. All these actions take time.

*   **Send packet CA->Netherlands->CA: 100 ms**

    E.g.: If we have a long-distance Zoom call, the latency might be around 100 ms.

*   **Retry/refresh internal: 1-10s**

    E.g: In a monitoring system, the refresh interval is usually set to 5~10 seconds (default value on Grafana).

## Notes

1 ns = 10^-9 seconds
1 us = 10^-6 seconds = 1,000 ns
1 ms = 10^-3 seconds = 1,000 us = 1,000,000 ns