High level design

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Event flow during user signin

this is only a notifcations service, so connecting to ws server on user login

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e2e JWT token flow

this is the e2e flow of the jwtToken from client to server, so that private function/procedures are properly authenticated through the token

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e2e post like and notification flow

this is the full e2e flow of what happens when user1 likes user2's post

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flow1

just after user1 likes user2's post there are two websocket events that are fired (1 inbound and 2 outbounds)

flow2

at first the inbound event (user1's client to the server) goes and does 2 tasks. one to update likes count in the db and the other is to asynchronously send the LIKE_POST event to the ws server.

flow3

then the ws server constructs a NOTIFICATION_EVENT to send to the post author client and a LIKE_ACK_EVENT to send to user1 client. therefore the ws server sends 2 outbound events (server to client)

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payload of the inbound (LIKE_POST) event

{
  "event": "LIKE_POST",
  "userId": "user1",
  "postId": "post2"
}

payload of the outbound (NOTIFICATION) event

{
  "event": "NOTIFICATION",
  "notification": {
    "type": "LIKE",
    "liked_by": "user2",
    "post_liked_on": "post1",
    "post_author": "user1"
  }
}

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