---
title: "Discussion on \"Latency Numbers Every Engineer Should Know\" | Hashnode"
description: "Discussion on \"Latency Numbers Every Engineer Should Know\". Latency is simply the time between asking for something and getting it back. Every system you will ever touch is built out of layers, and each layer has its own latency because each layer is physicall"
url: "https://hashnode.com/posts/latency-numbers-every-engineer-should-know/6a6df298c524163723383a5e"
---

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# [Latency Numbers Every Engineer Should Know](https://rabindranath-tiwari.com.np/latency-numbers-every-engineer-should-know?utm_source=hashnode&utm_medium=feed)

Latency is simply the time between asking for something and getting it back. Every system you will ever touch is built out of layers, and each layer has its own latency because each layer is physicall

Aug 1 · 5 min read · rabindranath-tiwari.com.np  
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## Written by

[Rohan Tiwari](https://hashnode.com/@tyranny)

@tyranny · Nepal

  
[View profile](https://hashnode.com/@tyranny)

Beyond Code

## Responses 3

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[Duko tools](https://hashnode.com/@talha24ramzan)

[Aug 3](https://hashnode.com/posts/latency-numbers-every-engineer-should-know/6a6df298c524163723383a5e/comment/6a7051224b60b36b2c546451)

The "scale everything up so L1 is 1 human second" trick is the one that actually makes this stick long-term, more than the raw nanosecond numbers ever do. Nanoseconds don't have intuition behind them, but "waiting years for a letter to come back" is something you can genuinely feel, which is probably why the metaphor survives in memory long after the exact numbers fade.

The tail-latency section is the sharper point for anyone past the junior-engineer stage, though. The math on 8 dependent calls each with their own p99 compounding to a ~7.7% chance of hitting at least one slow link is the kind of thing that's easy to nod along to in the abstract but genuinely surprising the first time you actually compute it against your own service's dependency chain. "Every individual service looks healthy on its own dashboard" while the aggregate p99 balloons is exactly the failure mode that makes tail latency so hard to debug organizationally, no single team's graphs show a problem, so the instinct is to assume there isn't one.

Worth citing Dean and Barroso directly too, since "The Tail at Scale" gets referenced constantly but read in full far less, the framing that tail latency, not average, becomes the dominant constraint at fleet scale is the actual thesis, not just a footnote on percentiles.

[Puneet Khandelwal](https://hashnode.com/@lifestyle4u)

[Aug 2](https://hashnode.com/posts/latency-numbers-every-engineer-should-know/6a6df298c524163723383a5e/comment/6a6f204798cbec36f3abd4a1)

LLove this perspective on prioritizing well-being

[Amit Joshi](https://hashnode.com/@DevNation)

[Aug 2](https://hashnode.com/posts/latency-numbers-every-engineer-should-know/6a6df298c524163723383a5e/comment/6a6eeabb0c8f047b17fe7220)

very informative, thanks for sharing.