Networking and APIsFormats
Why is the same order 48 bytes in JSON but 10 in Avro?
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More questions.
Data and storageHyperLogLog
How do you count 100 million unique users in just 12 KB?
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Messaging and streamsClean-up
Why can a forgotten outbox grow by 518 million rows a day?
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Running in productionMetastable
The network blip lasted 10 seconds. Why is the outage still going?
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Why is it slow? Performance anti-patternsInterview
Where should rider GPS pings go? Why not the orders database?
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Key technologiesDeterminism
Your deploy passed every test. Why did thousands of running orders just freeze?
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Core conceptsSafe retries
The pay call timed out. Did it charge you, or not?
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Networking and APIsIdentity
Why should the API never take a userId in the request body?
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Data and storageNear me
Why do latitude and longitude indexes read 1,500× more rows than they return?
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Messaging and streamsReplays
Why can rebuilding a read model text millions of customers?
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Running in productionFail open
Every server fails its health check at once. Should you remove them all?
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Why is it slow? Performance anti-patternsHTTP caching
How can one response header stop a menu being rebuilt a million times?
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Key technologiesBi-encoders
Pairing 10,000 sentences through BERT took 65 hours. How do vectors take 5 s?
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Core conceptsAsync request-reply
The export takes minutes. What should the API reply right away?
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Networking and APIsCritical path
Seven calls take 300 ms one by one. Why does the page take 130?
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Data and storageThe real test
“Which database would you use?” Why is a brand the wrong first answer?
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Running in productionShuffle sharding
Eight workers, one poison customer. Why do only 1 in 28 others go down?
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Why is it slow? Performance anti-patterns202 Accepted
Your report takes 90 seconds to build. What should the API return?
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Key technologiesKV cache
Why does one 4K-token chat hold 1.3 GB of GPU memory?
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Core conceptsReads vs writes
Writes are drowning your database. Why won’t ten more replicas help?
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Networking and APIsKeep-alive
Why do random 502s get worse when traffic is quiet?
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Data and storageMeasure first
How did one 4-second query eat 19.7 hours of database time a day?
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Running in productionCardinality
Why can one innocent label turn 70,000 metric series into 28 million?
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Why is it slow? Performance anti-patternsThe cliff
Your provider slowed to 190 ms. It isn’t down. Why are you?
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Key technologiesHot keys
Why can’t more shards save a flash sale’s hottest key?
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Core conceptsUtilisation
Why does going from 50% to 95% busy make responses 10× slower?
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