{"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":68,"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":35.7,"width":248,"height":28.6,"fontSize":22,"fontFamily":1,"text":"Presence System","originalText":"Presence System","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":128,"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":147.7,"width":248,"height":28.6,"fontSize":22,"fontFamily":1,"text":"Redis Cluster","originalText":"Redis Cluster","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":240,"width":288,"height":293.40000000000003,"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":258,"width":248,"height":257.40000000000003,"fontSize":22,"fontFamily":1,"text":"Key:\n\"presence:user_123\"\nValue: {\nstatus: \"online\",\nlast_active:\n1712160005,\ndevice: \"mobile\",\nws_server:\n\"ws-gateway-7\"","originalText":"Key:\n\"presence:user_123\"\nValue: {\nstatus: \"online\",\nlast_active:\n1712160005,\ndevice: \"mobile\",\nws_server:\n\"ws-gateway-7\"","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":577.4000000000001,"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-7","type":"text","seed":552,"x":36,"y":595.4000000000001,"width":248,"height":85.8,"fontSize":22,"fontFamily":1,"text":"TTL: 60 seconds\n(auto-expire to\noffline)","originalText":"TTL: 60 seconds\n(auto-expire to\noffline)","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":743.2,"width":288,"height":68,"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":762.9000000000001,"width":248,"height":28.6,"fontSize":22,"fontFamily":1,"text":"Heartbeat Protocol:","originalText":"Heartbeat Protocol:","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":855.2,"width":288,"height":207.6,"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":873.2,"width":248,"height":171.6,"fontSize":22,"fontFamily":1,"text":"Client sends\nheartbeat every 30\nseconds\nServer refreshes\nRedis TTL on each\nbeat","originalText":"Client sends\nheartbeat every 30\nseconds\nServer refreshes\nRedis TTL on each\nbeat","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":1106.8,"width":288,"height":179,"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":1124.8,"width":248,"height":143,"fontSize":22,"fontFamily":1,"text":"Client --PING--> WS\nServer --SET+TTL-->\nRedis\nClient <--PONG-- WS\nServer","originalText":"Client --PING--> WS\nServer --SET+TTL-->\nRedis\nClient <--PONG-- WS\nServer","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":1329.8,"width":288,"height":236.20000000000002,"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":1347.8,"width":248,"height":200.20000000000002,"fontSize":22,"fontFamily":1,"text":"If heartbeat stops:\nRedis TTL expires\nafter 60s\nStatus automatically\nbecomes \"offline\"\nPublish event to\npresence subscribers","originalText":"If heartbeat stops:\nRedis TTL expires\nafter 60s\nStatus automatically\nbecomes \"offline\"\nPublish event to\npresence subscribers","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":1610,"width":288,"height":68,"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":1629.7,"width":248,"height":28.6,"fontSize":22,"fontFamily":1,"text":"Presence Fan-Out:","originalText":"Presence Fan-Out:","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":1722,"width":288,"height":322,"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":1740,"width":248,"height":286,"fontSize":22,"fontFamily":1,"text":"When user A goes\nonline/offline:\n1. Get A's contact\nlist (friends/group\nmates)\n2. For each ONLINE\ncontact:\n→ Push presence\nupdate via\nWebSocket","originalText":"When user A goes\nonline/offline:\n1. Get A's contact\nlist (friends/group\nmates)\n2. For each ONLINE\ncontact:\n→ Push presence\nupdate via\nWebSocket","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":2088,"width":288,"height":322,"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":2106,"width":248,"height":286,"fontSize":22,"fontFamily":1,"text":"Optimization for\nlarge friend lists:\nOnly push to\ncontacts who have A\nvisible\n(chat window open or\nrecent conversation)\nBatch updates\n(debounce rapid\non/off)","originalText":"Optimization for\nlarge friend lists:\nOnly push to\ncontacts who have A\nvisible\n(chat window open or\nrecent conversation)\nBatch updates\n(debounce rapid\non/off)","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":2454,"width":288,"height":264.8,"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":2472,"width":248,"height":228.8,"fontSize":22,"fontFamily":1,"text":"WhatsApp approach:\n\"last seen\" on\ndemand\n→ Client queries\npresence when opening\nchat\n→ No push, saves\nbandwidth","originalText":"WhatsApp approach:\n\"last seen\" on\ndemand\n→ Client queries\npresence when opening\nchat\n→ No push, saves\nbandwidth","textAlign":"left","verticalAlign":"middle","containerId":"shape-22","lineHeight":1.3,"autoResize":false,"customData":{"revealStep":12}}],"appState":{"viewBackgroundColor":"#fbfbf8","gridSize":null},"files":{}}