{"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":"New post by\nUser X","originalText":"New post by\nUser X","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"}],"updated":0,"link":null,"locked":false,"id":"shape-2","type":"rectangle","seed":187,"x":16,"y":153.2,"width":288,"height":293.40000000000003,"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":257.40000000000003,"fontSize":22,"fontFamily":1,"text":"Use Fanout-on-Write\n- When they post,\nwrite to all\nfollowers' feeds\n- Fast: < 10K writes\nper post\n- Followers see new\nposts instantly in\ncached feed","originalText":"Use Fanout-on-Write\n- When they post,\nwrite to all\nfollowers' feeds\n- Fast: < 10K writes\nper post\n- Followers see new\nposts instantly in\ncached feed","textAlign":"left","verticalAlign":"middle","containerId":"shape-2","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-5"},{"type":"arrow","id":"shape-6"}],"updated":0,"link":null,"locked":false,"id":"shape-4","type":"rectangle","seed":333,"x":16,"y":490.6,"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-5","type":"text","seed":406,"x":36,"y":508.6,"width":248,"height":57.2,"fontSize":22,"fontFamily":1,"text":"New post by\nUser X","originalText":"New post by\nUser X","textAlign":"left","verticalAlign":"middle","containerId":"shape-4","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-6","type":"arrow","seed":479,"x":36,"y":597.8000000000001,"width":0,"height":28,"points":[[0,0],[0,28]],"lastCommittedPoint":null,"startBinding":{"elementId":"shape-4","focus":0,"gap":14},"endBinding":{"elementId":"shape-7","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-8"},{"type":"arrow","id":"shape-6"}],"updated":0,"link":null,"locked":false,"id":"shape-7","type":"rectangle","seed":552,"x":16,"y":639.8000000000001,"width":288,"height":121.8,"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":657.8000000000001,"width":248,"height":85.8,"fontSize":22,"fontFamily":1,"text":"X has > 10K\n+----------->\nfollowers?","originalText":"X has > 10K\n+----------->\nfollowers?","textAlign":"left","verticalAlign":"middle","containerId":"shape-7","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-10"},{"type":"arrow","id":"shape-11"}],"updated":0,"link":null,"locked":false,"id":"shape-9","type":"rectangle","seed":698,"x":16,"y":805.6,"width":288,"height":121.8,"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-10","type":"text","seed":771,"x":36,"y":823.6,"width":248,"height":85.8,"fontSize":22,"fontFamily":1,"text":"X has > 10K\n+----------->\nfollowers?","originalText":"X has > 10K\n+----------->\nfollowers?","textAlign":"left","verticalAlign":"middle","containerId":"shape-9","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-11","type":"arrow","seed":844,"x":36,"y":941.4,"width":0,"height":28,"points":[[0,0],[0,28]],"lastCommittedPoint":null,"startBinding":{"elementId":"shape-9","focus":0,"gap":14},"endBinding":{"elementId":"shape-12","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-13"},{"type":"arrow","id":"shape-11"}],"updated":0,"link":null,"locked":false,"id":"shape-12","type":"rectangle","seed":917,"x":16,"y":983.4,"width":288,"height":121.8,"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":1001.4,"width":248,"height":85.8,"fontSize":22,"fontFamily":1,"text":"Fanout to all\nfollowers' feed\ncaches (Redis)","originalText":"Fanout to all\nfollowers' feed\ncaches (Redis)","textAlign":"left","verticalAlign":"middle","containerId":"shape-12","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-15"}],"updated":0,"link":null,"locked":false,"id":"shape-14","type":"rectangle","seed":1063,"x":16,"y":1149.2,"width":288,"height":121.8,"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-15","type":"text","seed":1136,"x":36,"y":1167.2,"width":248,"height":85.8,"fontSize":22,"fontFamily":1,"text":"Store post only.\nNo fanout.\nMark X as \"celebrity\"","originalText":"Store post only.\nNo fanout.\nMark X as \"celebrity\"","textAlign":"left","verticalAlign":"middle","containerId":"shape-14","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":5}},{"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-6"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-17"}],"updated":0,"link":null,"locked":false,"id":"shape-16","type":"rectangle","seed":1209,"x":16,"y":1315,"width":288,"height":550.8000000000001,"customData":{"revealStep":6}},{"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-6"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-17","type":"text","seed":1282,"x":36,"y":1333,"width":248,"height":514.8000000000001,"fontSize":22,"fontFamily":1,"text":"Use Fanout-on-Read\n- When they post,\njust store the post\n- NO fanout to\nmillions of followers\n- When a follower\nopens feed:\n1. Read pre-computed\nfeed from cache\n(normal posts)\n2. Fetch recent\nposts from followed\ncelebrities\n3. Merge celebrity\nposts into cached\nfeed\n4. Return combined\nfeed","originalText":"Use Fanout-on-Read\n- When they post,\njust store the post\n- NO fanout to\nmillions of followers\n- When a follower\nopens feed:\n1. Read pre-computed\nfeed from cache\n(normal posts)\n2. Fetch recent\nposts from followed\ncelebrities\n3. Merge celebrity\nposts into cached\nfeed\n4. Return combined\nfeed","textAlign":"left","verticalAlign":"middle","containerId":"shape-16","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":6}},{"angle":0,"strokeColor":"#a68a53","backgroundColor":"#fff7e6","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-7"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-19"}],"updated":0,"link":null,"locked":false,"id":"shape-18","type":"rectangle","seed":1355,"x":16,"y":1909.8000000000002,"width":288,"height":1580.4,"customData":{"revealStep":7}},{"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-7"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-19","type":"text","seed":1428,"x":36,"y":1927.8000000000002,"width":248,"height":1544.4,"fontSize":22,"fontFamily":1,"text":"Hybrid Fanout\nStrategy\n(Recommended)\n\nDivide users into two\ncategories:\n\nNormal users (< 10K\nfollowers):\n\nCelebrity users (>\n10K followers):\n\nFeed generation (for\nUser B):\n\nStep 1: Read B's\ncached feed (from\nfanout-on-write)\n[post_3, post_7,\npost_12, ...]\n(posts from normal\nusers B follows)\n\nStep 2: Get B's\ncelebrity following list\n[celeb_A, celeb_B,\nceleb_C]\n\nStep 3: Fetch recent\nposts from each\ncelebrity\nceleb_A: [post_100,\npost_101]\nceleb_B:\n[post_200]\nceleb_C: [post_300,\npost_301]\n\nStep 4: Merge all\nposts, sort/rank,\nreturn top N\n\nTotal queries: 1\ncache read + ~5-10\ncelebrity reads\nMuch better than\n200+ reads (pure\npull) or\n100M writes (pure\npush for celebs)\n\nDecision flow for a\nnew post:","originalText":"Hybrid Fanout\nStrategy\n(Recommended)\n\nDivide users into two\ncategories:\n\nNormal users (< 10K\nfollowers):\n\nCelebrity users (>\n10K followers):\n\nFeed generation (for\nUser B):\n\nStep 1: Read B's\ncached feed (from\nfanout-on-write)\n[post_3, post_7,\npost_12, ...]\n(posts from normal\nusers B follows)\n\nStep 2: Get B's\ncelebrity following list\n[celeb_A, celeb_B,\nceleb_C]\n\nStep 3: Fetch recent\nposts from each\ncelebrity\nceleb_A: [post_100,\npost_101]\nceleb_B:\n[post_200]\nceleb_C: [post_300,\npost_301]\n\nStep 4: Merge all\nposts, sort/rank,\nreturn top N\n\nTotal queries: 1\ncache read + ~5-10\ncelebrity reads\nMuch better than\n200+ reads (pure\npull) or\n100M writes (pure\npush for celebs)\n\nDecision flow for a\nnew post:","textAlign":"left","verticalAlign":"middle","containerId":"shape-18","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":7}}],"appState":{"viewBackgroundColor":"#fbfbf8","gridSize":null},"files":{}}