Interview Q&A / System Design
System Design interview questions
Caching, scaling, databases and classic design problems for beginners.
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- What is the difference between SLI, SLO and SLA?
An SLI is a measured number like request success rate. An SLO is the internal target for that number, such as 99.9%. An SLA is the contract with customers that promises a level and usually names a penalty if missed.
BeginnerQuick answer1 min read - Why do engineers track p95 and p99 latency instead of the average?
Averages hide slow outliers. p99 means 99% of requests were faster than this value, so it shows what your unluckiest users feel, which is what drives complaints and timeouts.
BeginnerQuick answer1 min read