Core conceptsShared fate
Facebook’s DNS servers were running. Why could nobody reach them?
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More questions.
Networking and APIsHyrum’s Law
Your list never promised an order. Why does changing it break someone?
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Data and storageResharding
Why does adding a fifth database server move 80% of your rows?
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Messaging and streamsRetention
Why did a lagging consumer group quietly skip days of orders?
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Running in productionJitter
Every client backs off politely. Why do retries still arrive in waves?
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Why is it slow? Performance anti-patternsSteal time
Your service changed nothing. Why does the same code suddenly run slower?
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Architecture stylesFree-riders
What stops you downloading the whole file and never uploading a byte?
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Key technologiesHot prefixes
S3 is practically unlimited. So why does it throttle your log pipeline?
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Common patternsHolds
Payment takes minutes. How do you hold a seat without a minutes-long lock?
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InfrastructureReplay
Your search indexer shipped a bug at 20:00. Can you replay the evening?
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Social & feedsVotes
Your vote shows instantly. Why does everyone else see it seconds later?
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Core conceptsData loss
The app said “payment successful”. Why is the record on a dead machine?
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Networking and APIsgRPC on the wire
Same order, 65 bytes as JSON, 9 as protobuf. Where did the rest go?
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Data and storageReplica lag
You tap Save, the page reloads, and your old address is back. Why?
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Messaging and streamsDead-letter queues
Why would a 10-minute outage dead-letter 450,000 good messages?
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Running in productionScope
One of four shards dies. Why can’t a single breaker get it right?
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Why is it slow? Performance anti-patternsTatkal
Why does refreshing a slow page keep it slow after the rush ends?
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Architecture stylesHybrids
One delivery app, six architecture styles. Why not just pick one?
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Key technologiesMemory
100 million embeddings need 307 GB of RAM. How do you shrink it 32×?
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Common patternsSizing
1,800 exports an hour, 2 minutes each. How many workers do you need?
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InfrastructureTime zones
Your cron job says 02:30. What happens on the night 02:30 doesn’t exist?
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Social & feedsDecks
Why is the next card already waiting when you swipe?
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Core conceptsFault models
Why does surviving one lying node take four replicas, not three?
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Networking and APIsPolling
Why do a million apps make 200,000 requests a second, mostly for nothing?
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Data and storageQuorums
Your write reached two of three copies. Will the next read see it?
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Messaging and streamsHot keys
One cricket match, 2,000 events a second. Why does its lane drown?
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