Azure System Design
System design on Azure, one real-world problem at a time: what broke or what had to be built, the query or trade-off that decided it, and the design that held.
4 parts · about 94 minutes end to end · updated October 3, 2026
Every Azure architecture diagram looks calm. The interesting part is the day it meets real users: a flash sale that sends 400,000 people to one page, a double tap that charges a customer twice, three hotel suppliers that describe the same room in three different ways. This series takes one of those problems at a time and designs the system that survives it.
Each part follows the same shape, because that is how design decisions are actually made: the problem as the business saw it, the query or measurement that showed what was really happening, the design that fixed it and why the obvious alternatives were wrong, how efficient the result is, and the guardrail that keeps it working. The SQL, KQL and C# are copy-pasteable. The judgement calls, what to cache and what never to, where a rule must live, when to wait and when to stop waiting, are the part you cannot get from a doc page. Every part ends with the system design interview questions it prepares you for.
Read it in order
- 1 Browsing Without a Login Was the Requirement: How to Secure a Public API on Azure
Browsing products without login was a real requirement. Trusting requests because they came from our own app was the bug, and curl does not care.
September 27, 2026 · 20 min read views
- 2 The Flash Sale That Hit the Database: When to Use Azure Managed Redis
When to use Azure Managed Redis, which replaces Azure Cache for Redis, learned from a flash sale that hit Azure SQL 2,200 times a second.
September 29, 2026 · 30 min read views
- 3 The Flash Sale That Ran Out of Bandwidth: When to Use a CDN on Azure
When to use a CDN on Azure, from a flash sale where one App Service served 1.6 million photo downloads. What to cache, and what never to.
September 30, 2026 · 21 min read views
- 4 Paid, Then Sold Out: How Hotel Booking Confirmation Really Works
How hotel booking confirmation works after payment: authorize, book with the supplier, then capture, and what happens if another site sells the room first.
October 3, 2026 · 24 min read views
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