{"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":121.8,"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":85.8,"fontSize":22,"fontFamily":1,"text":"Scheduled &\nTimezone-Aware\nDelivery","originalText":"Scheduled &\nTimezone-Aware\nDelivery","textAlign":"left","verticalAlign":"middle","containerId":"shape-0","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":1}},{"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-3"}],"updated":0,"link":null,"locked":false,"id":"shape-2","type":"rectangle","seed":187,"x":16,"y":181.8,"width":288,"height":68,"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":201.5,"width":248,"height":28.6,"fontSize":22,"fontFamily":1,"text":"Scheduling Service:","originalText":"Scheduling Service:","textAlign":"left","verticalAlign":"middle","containerId":"shape-2","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":2}},{"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-3"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-5"}],"updated":0,"link":null,"locked":false,"id":"shape-4","type":"rectangle","seed":333,"x":16,"y":293.8,"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-5","type":"text","seed":406,"x":36,"y":311.8,"width":248,"height":171.6,"fontSize":22,"fontFamily":1,"text":"Notifications with\nschedule_at are\nstored in a\nscheduled queue, not\nsent\nimmediately.","originalText":"Notifications with\nschedule_at are\nstored in a\nscheduled queue, not\nsent\nimmediately.","textAlign":"left","verticalAlign":"middle","containerId":"shape-4","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":3}},{"angle":0,"strokeColor":"#9180ac","backgroundColor":"#f4effb","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-7"}],"updated":0,"link":null,"locked":false,"id":"shape-6","type":"rectangle","seed":479,"x":16,"y":545.4,"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-7","type":"text","seed":552,"x":36,"y":563.4,"width":248,"height":57.2,"fontSize":22,"fontFamily":1,"text":"Implementation\noptions:","originalText":"Implementation\noptions:","textAlign":"left","verticalAlign":"middle","containerId":"shape-6","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-9"}],"updated":0,"link":null,"locked":false,"id":"shape-8","type":"rectangle","seed":625,"x":16,"y":682.6,"width":288,"height":379.2,"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-9","type":"text","seed":698,"x":36,"y":700.6,"width":248,"height":343.2,"fontSize":22,"fontFamily":1,"text":"Option A: Database\npolling\nStore in\nscheduled_notificatio\nns table\nCron job queries\nevery 30s:\nWHERE send_at <=\nNOW() AND\nstatus=PENDING\nSimple but polling =\nwasteful","originalText":"Option A: Database\npolling\nStore in\nscheduled_notificatio\nns table\nCron job queries\nevery 30s:\nWHERE send_at <=\nNOW() AND\nstatus=PENDING\nSimple but polling =\nwasteful","textAlign":"left","verticalAlign":"middle","containerId":"shape-8","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":5}},{"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-6"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-11"}],"updated":0,"link":null,"locked":false,"id":"shape-10","type":"rectangle","seed":771,"x":16,"y":1105.8,"width":288,"height":379.2,"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-11","type":"text","seed":844,"x":36,"y":1123.8,"width":248,"height":343.2,"fontSize":22,"fontFamily":1,"text":"Option B: Redis\nsorted set ⭐\nZADD\nscheduled:{shard}\nsend_time notif_id\nWorker:\nZRANGEBYSCORE 0\n{now}\nO(log N) operations,\nno polling waste\nShard by user_id %\n64 for scale","originalText":"Option B: Redis\nsorted set ⭐\nZADD\nscheduled:{shard}\nsend_time notif_id\nWorker:\nZRANGEBYSCORE 0\n{now}\nO(log N) operations,\nno polling waste\nShard by user_id %\n64 for scale","textAlign":"left","verticalAlign":"middle","containerId":"shape-10","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-13"}],"updated":0,"link":null,"locked":false,"id":"shape-12","type":"rectangle","seed":917,"x":16,"y":1529,"width":288,"height":264.8,"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-13","type":"text","seed":990,"x":36,"y":1547,"width":248,"height":228.8,"fontSize":22,"fontFamily":1,"text":"Option C: Kafka\ndelayed topics\nNot natively\nsupported\nCan simulate with\nconsumer that holds\nmessages until\nsend_time","originalText":"Option C: Kafka\ndelayed topics\nNot natively\nsupported\nCan simulate with\nconsumer that holds\nmessages until\nsend_time","textAlign":"left","verticalAlign":"middle","containerId":"shape-12","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":7}},{"angle":0,"strokeColor":"#9180ac","backgroundColor":"#f4effb","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-8"],"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":1837.8,"width":288,"height":93.2,"customData":{"revealStep":8}},{"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-8"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-15","type":"text","seed":1136,"x":36,"y":1855.8,"width":248,"height":57.2,"fontSize":22,"fontFamily":1,"text":"Timezone-Aware\n\"Best Time to Send\":","originalText":"Timezone-Aware\n\"Best Time to Send\":","textAlign":"left","verticalAlign":"middle","containerId":"shape-14","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":8}},{"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-9"],"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":1975,"width":288,"height":93.2,"customData":{"revealStep":9}},{"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-9"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-17","type":"text","seed":1282,"x":36,"y":1993,"width":248,"height":57.2,"fontSize":22,"fontFamily":1,"text":"\"Send at 9 AM\nuser's local time\"","originalText":"\"Send at 9 AM\nuser's local time\"","textAlign":"left","verticalAlign":"middle","containerId":"shape-16","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":9}},{"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-10"],"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":2112.2,"width":288,"height":436.40000000000003,"customData":{"revealStep":10}},{"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-10"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-19","type":"text","seed":1428,"x":36,"y":2130.2,"width":248,"height":400.40000000000003,"fontSize":22,"fontFamily":1,"text":"1. Group users by\ntimezone\nUTC-8 (PST): 50M\nusers → 9 AM = 5\nPM UTC\nUTC-5 (EST): 80M\nusers → 9 AM = 2\nPM UTC\nUTC+0 (GMT): 30M\nusers → 9 AM = 9\nAM UTC\nUTC+5:30 (IST):\n100M users → 9 AM =\n3:30 AM UTC","originalText":"1. Group users by\ntimezone\nUTC-8 (PST): 50M\nusers → 9 AM = 5\nPM UTC\nUTC-5 (EST): 80M\nusers → 9 AM = 2\nPM UTC\nUTC+0 (GMT): 30M\nusers → 9 AM = 9\nAM UTC\nUTC+5:30 (IST):\n100M users → 9 AM =\n3:30 AM UTC","textAlign":"left","verticalAlign":"middle","containerId":"shape-18","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":10}},{"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-11"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-21"}],"updated":0,"link":null,"locked":false,"id":"shape-20","type":"rectangle","seed":1501,"x":16,"y":2592.6,"width":288,"height":236.20000000000002,"customData":{"revealStep":11}},{"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-11"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-21","type":"text","seed":1574,"x":36,"y":2610.6,"width":248,"height":200.20000000000002,"fontSize":22,"fontFamily":1,"text":"2. Schedule separate\nbatch per TZ bucket\n3. Each batch\nenqueued at the\nright UTC\ntime for that\ntimezone","originalText":"2. Schedule separate\nbatch per TZ bucket\n3. Each batch\nenqueued at the\nright UTC\ntime for that\ntimezone","textAlign":"left","verticalAlign":"middle","containerId":"shape-20","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":11}},{"angle":0,"strokeColor":"#9180ac","backgroundColor":"#f4effb","fillStyle":"solid","strokeWidth":1.5,"strokeStyle":"solid","roughness":0.7,"opacity":100,"version":1,"versionNonce":1,"isDeleted":false,"groupIds":["step-12"],"frameId":null,"roundness":null,"boundElements":[{"type":"text","id":"shape-23"}],"updated":0,"link":null,"locked":false,"id":"shape-22","type":"rectangle","seed":1647,"x":16,"y":2872.7999999999997,"width":288,"height":150.4,"customData":{"revealStep":12}},{"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-12"],"frameId":null,"roundness":null,"boundElements":null,"updated":0,"link":null,"locked":false,"id":"shape-23","type":"text","seed":1720,"x":36,"y":2890.7999999999997,"width":248,"height":114.4,"fontSize":22,"fontFamily":1,"text":"~24 timezone\nbuckets\nStagger slightly to\navoid thundering herd","originalText":"~24 timezone\nbuckets\nStagger slightly to\navoid thundering herd","textAlign":"left","verticalAlign":"middle","containerId":"shape-22","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":12}}],"appState":{"viewBackgroundColor":"#fbfbf8","gridSize":null},"files":{}}