Suthahar Jegatheesan MSDEVBUILD / blog Multi-Stack Dev Build · by Suthahar
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One line of code. Seven stops.

What really happens between await http.GetAsync(...) and the JSON landing back in your app.

What you'll learn

  • The seven stops every HTTP call to an Azure API makes, and what each one costs
  • Why the first call is slow: 100 of the 160 ms is DNS and the TLS handshake, before your code runs
  • Why new HttpClient() in a loop pays that cost forever, and IHttpClientFactory pays it once
Azure 13 steps 64 seconds —views

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Understand it one step at a time

The short runs these in order in about 64 seconds. Here they are written out — pick any step to jump the short straight to it.

1 Step 1 of 13

One line of code

You call an API with one line of code and get JSON back. Between those two moments, seven separate hops actually happen.

Frequently asked questions

Why is the first call to an Azure API so much slower than the rest?
Most of that latency — around 100 of a roughly 160 ms first call — is DNS resolution and the TLS handshake, both of which happen before any of your code runs. Once the connection exists, later calls skip straight past that cost.
Why does new HttpClient() in a loop hurt performance?
It pays the DNS-and-TLS setup cost on every single call instead of once. IHttpClientFactory reuses the underlying connection, so that cost is paid once and every subsequent request is faster.

Free app · no app store

These are built for a phone

Every short is drawn at full portrait height, the shape a phone already is. Installed, it opens full-bleed with no address bar across the top — and the whole library reads offline.

How it works

Read deeper on Azure

Twenty seconds gets the shape of an idea across. These go into how it behaves in production.

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