{"type":"excalidraw","version":2,"source":"https://AwesomeSystemDesign.dev","elements":[{"angle":0,"strokeColor":"#6577aa","backgroundColor":"#eef1fc","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-1"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-1"}],"updated":0,"link":null,"locked":false,"id":"shape-0","type":"rectangle","seed":41,"x":16,"y":16,"width":288,"height":93.2,"customData":{"revealStep":1}},{"angle":0,"strokeColor":"#394557","backgroundColor":"transparent","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-1"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-1","type":"text","seed":114,"x":36,"y":34,"width":248,"height":57.2,"fontSize":22,"fontFamily":1,"text":"Event\n\"celeb posts\"","originalText":"Event\n\"celeb posts\"","textAlign":"left","verticalAlign":"middle","containerId":"shape-0","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":1}},{"angle":0,"strokeColor":"#6577aa","backgroundColor":"#eef1fc","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-2"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-3"},{"type":"arrow","id":"shape-4"}],"updated":0,"link":null,"locked":false,"id":"shape-2","type":"rectangle","seed":187,"x":16,"y":153.2,"width":288,"height":93.2,"customData":{"revealStep":2}},{"angle":0,"strokeColor":"#394557","backgroundColor":"transparent","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-2"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-3","type":"text","seed":260,"x":36,"y":171.2,"width":248,"height":57.2,"fontSize":22,"fontFamily":1,"text":"Event\n\"celeb posts\"","originalText":"Event\n\"celeb posts\"","textAlign":"left","verticalAlign":"middle","containerId":"shape-2","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":2}},{"angle":0,"strokeColor":"#6577aa","backgroundColor":"transparent","fillStyle":"solid","strokeWidth":2,"strokeStyle":"solid","roughness":0.4,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-2"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-4","type":"arrow","seed":333,"x":36,"y":260.4,"width":0,"height":28,"points":[[0,0],[0,28]],"lastCommittedPoint":null,"startBinding":{"elementId":"shape-2","focus":0,"gap":14},"endBinding":{"elementId":"shape-5","focus":0,"gap":14},"startArrowhead":null,"endArrowhead":"arrow","elbowed":false,"customData":{"revealStep":2}},{"angle":0,"strokeColor":"#628572","backgroundColor":"#edf5ee","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-2"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-6"},{"type":"arrow","id":"shape-4"}],"updated":0,"link":null,"locked":false,"id":"shape-5","type":"rectangle","seed":406,"x":16,"y":302.4,"width":288,"height":236.20000000000002,"customData":{"revealStep":2}},{"angle":0,"strokeColor":"#394557","backgroundColor":"transparent","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-2"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-6","type":"text","seed":479,"x":36,"y":320.4,"width":248,"height":200.20000000000002,"fontSize":22,"fontFamily":1,"text":"Fanout\nService\n\nSplit\n50M into\n50K\nchunks","originalText":"Fanout\nService\n\nSplit\n50M into\n50K\nchunks","textAlign":"left","verticalAlign":"middle","containerId":"shape-5","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":2}},{"angle":0,"strokeColor":"#6577aa","backgroundColor":"#eef1fc","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-3"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-8"},{"type":"arrow","id":"shape-9"}],"updated":0,"link":null,"locked":false,"id":"shape-7","type":"rectangle","seed":552,"x":16,"y":582.6,"width":288,"height":93.2,"customData":{"revealStep":3}},{"angle":0,"strokeColor":"#394557","backgroundColor":"transparent","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-3"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-8","type":"text","seed":625,"x":36,"y":600.6,"width":248,"height":57.2,"fontSize":22,"fontFamily":1,"text":"Fanout\nService","originalText":"Fanout\nService","textAlign":"left","verticalAlign":"middle","containerId":"shape-7","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":3}},{"angle":0,"strokeColor":"#6577aa","backgroundColor":"transparent","fillStyle":"solid","strokeWidth":2,"strokeStyle":"solid","roughness":0.4,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-3"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-9","type":"arrow","seed":698,"x":36,"y":689.8000000000001,"width":0,"height":28,"points":[[0,0],[0,28]],"lastCommittedPoint":null,"startBinding":{"elementId":"shape-7","focus":0,"gap":14},"endBinding":{"elementId":"shape-10","focus":0,"gap":14},"startArrowhead":null,"endArrowhead":"arrow","elbowed":false,"customData":{"revealStep":3}},{"angle":0,"strokeColor":"#628572","backgroundColor":"#edf5ee","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-3"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-11"},{"type":"arrow","id":"shape-9"}],"updated":0,"link":null,"locked":false,"id":"shape-10","type":"rectangle","seed":771,"x":16,"y":731.8000000000001,"width":288,"height":207.6,"customData":{"revealStep":3}},{"angle":0,"strokeColor":"#394557","backgroundColor":"transparent","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-3"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-11","type":"text","seed":844,"x":36,"y":749.8000000000001,"width":248,"height":171.6,"fontSize":22,"fontFamily":1,"text":"Kafka\npush topic\n\n50K messages\n(1K users\nper msg)","originalText":"Kafka\npush topic\n\n50K messages\n(1K users\nper msg)","textAlign":"left","verticalAlign":"middle","containerId":"shape-10","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":3}},{"angle":0,"strokeColor":"#6577aa","backgroundColor":"#eef1fc","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-4"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-13"},{"type":"arrow","id":"shape-14"}],"updated":0,"link":null,"locked":false,"id":"shape-12","type":"rectangle","seed":917,"x":16,"y":983.4000000000001,"width":288,"height":93.2,"customData":{"revealStep":4}},{"angle":0,"strokeColor":"#394557","backgroundColor":"transparent","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-4"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-13","type":"text","seed":990,"x":36,"y":1001.4000000000001,"width":248,"height":57.2,"fontSize":22,"fontFamily":1,"text":"Kafka\npush topic","originalText":"Kafka\npush topic","textAlign":"left","verticalAlign":"middle","containerId":"shape-12","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":4}},{"angle":0,"strokeColor":"#6577aa","backgroundColor":"transparent","fillStyle":"solid","strokeWidth":2,"strokeStyle":"solid","roughness":0.4,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-4"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-14","type":"arrow","seed":1063,"x":36,"y":1090.6000000000001,"width":0,"height":28,"points":[[0,0],[0,28]],"lastCommittedPoint":null,"startBinding":{"elementId":"shape-12","focus":0,"gap":14},"endBinding":{"elementId":"shape-15","focus":0,"gap":14},"startArrowhead":null,"endArrowhead":"arrow","elbowed":false,"customData":{"revealStep":4}},{"angle":0,"strokeColor":"#628572","backgroundColor":"#edf5ee","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-4"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-16"},{"type":"arrow","id":"shape-14"}],"updated":0,"link":null,"locked":false,"id":"shape-15","type":"rectangle","seed":1136,"x":16,"y":1132.6000000000001,"width":288,"height":150.4,"customData":{"revealStep":4}},{"angle":0,"strokeColor":"#394557","backgroundColor":"transparent","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-4"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-16","type":"text","seed":1209,"x":36,"y":1150.6000000000001,"width":248,"height":114.4,"fontSize":22,"fontFamily":1,"text":"Push Workers (100)\nEach processes 1K\nusers\n→ APNs/FCM calls","originalText":"Push Workers (100)\nEach processes 1K\nusers\n→ APNs/FCM calls","textAlign":"left","verticalAlign":"middle","containerId":"shape-15","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":4}},{"angle":0,"strokeColor":"#6577aa","backgroundColor":"#eef1fc","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-5"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-18"}],"updated":0,"link":null,"locked":false,"id":"shape-17","type":"rectangle","seed":1282,"x":16,"y":1327.0000000000002,"width":288,"height":1551.8,"customData":{"revealStep":5}},{"angle":0,"strokeColor":"#394557","backgroundColor":"transparent","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-5"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-18","type":"text","seed":1355,"x":36,"y":1345.0000000000002,"width":248,"height":1515.8,"fontSize":22,"fontFamily":1,"text":"Fanout-on-Write\n\nWhen event occurs →\nimmediately enqueue\none\nnotification\nper recipient into\ntheir individual queue.\n\nEvent: \"User A liked\nUser B's photo\"\n\n1. Notification Service\nreceives event\n2. Look up: who\nneeds to be notified?\n→ [User B]\n3. Write notification\nto User B's feed in\nDB\n4. Enqueue push to\nKafka for User B\n\nFor broadcast (50M\nfollowers):\n1. Notification Service\nreceives event\n2. Look up: who\nfollows the celebrity?\n→ [50M users]\n3. Partition follower\nlist into chunks\n(1000 each)\n4. Enqueue 50K\nfanout tasks into\nKafka\n5. Each worker\nprocesses 1 chunk →\n1000 notifications\n\n✅ Recipients get\nnotification\nimmediately\n✅ Simple read path\n(just read user's\nfeed)\n❌ Slow for\nhigh-follower\naccounts (fanout\ndelay)\n❌ Wasteful for\ninactive users who\nnever check","originalText":"Fanout-on-Write\n\nWhen event occurs →\nimmediately enqueue\none\nnotification\nper recipient into\ntheir individual queue.\n\nEvent: \"User A liked\nUser B's photo\"\n\n1. Notification Service\nreceives event\n2. Look up: who\nneeds to be notified?\n→ [User B]\n3. Write notification\nto User B's feed in\nDB\n4. Enqueue push to\nKafka for User B\n\nFor broadcast (50M\nfollowers):\n1. Notification Service\nreceives event\n2. Look up: who\nfollows the celebrity?\n→ [50M users]\n3. Partition follower\nlist into chunks\n(1000 each)\n4. Enqueue 50K\nfanout tasks into\nKafka\n5. Each worker\nprocesses 1 chunk →\n1000 notifications\n\n✅ Recipients get\nnotification\nimmediately\n✅ Simple read path\n(just read user's\nfeed)\n❌ Slow for\nhigh-follower\naccounts (fanout\ndelay)\n❌ Wasteful for\ninactive users who\nnever check","textAlign":"left","verticalAlign":"middle","containerId":"shape-17","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":5}}],"appState":{"viewBackgroundColor":"#fbfbf8","gridSize":null},"files":{}}