Interview Q&A / System Design
System Design interview questions
Caching, scaling, databases and classic design problems for beginners.
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- What is a dead letter queue and when do you use one?
A dead letter queue holds messages that failed processing after the allowed retries. It stops one bad message from blocking the queue forever and keeps the message for inspection and later reprocessing.
BeginnerQuick answer1 min read - What is a single point of failure and how do you remove it?
A single point of failure is one component whose failure takes the whole system down. You remove it with redundancy: run several copies, add failover, and spread them across machines and zones.
BeginnerQuick answer1 min read - 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