Guides
Questions about capacity, latency and cost, answered with numbers: our own measurements on cloud machines, the arithmetic behind them, and designs you can run in Stackrig. Every guide states its setup and what it does not tell you. Newest first.
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Why does fan-out make fast services slow?
A request that waits for 100 parallel calls is as slow as the slowest of them: the arithmetic of Dean and Barroso's paper, and the same effect in a design you can run.
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Why does p99 latency explode long before 100 % CPU?
The queueing arithmetic for 1, 2 and 16 cores, what bursts do to it, our Postgres measurement, and the same curve in four designs you can open.
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How many users can a $12 server handle? We measured it
A $12-a-month VM with Nginx, Node.js and Postgres under virtual users: about 800 users at one second of think time, and a CPU throttle the guest does not show.
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How many requests per second can one Postgres handle?
One PostgreSQL on a 2-vCPU VM, measured: about 6,000 simple indexed reads per second at 100 % CPU, where p99 starts to climb, and how to estimate your own number.
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How big should your database connection pool be?
A pool of 4 against a pool of 16 connections on the same Postgres, measured, and Little's law for sizing your own.
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Cache hit ratio: what 80 % vs 95 % means for your database
The arithmetic of cache misses, and what a cold cache after a restart does to the database behind it.
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Retry storms: why retries take your service down
How retries multiply load, why a storm can outlive its trigger, and the fixes that work, shown in a design you can run.
, updated
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System design interview: the URL shortener, simulated live
The classic interview design with its numbers simulated over a real day of traffic: what breaks first, at which load, and what it costs.
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How closely the live model agrees with an exact simulation is on How accurate is Stackrig?