Like Notifications

Overview

1. Mobile user likes some content
2. POST request to /likes
3. Backend inserts Like row into table
4. Backend creates Notification row in table
5. Backend sends a message to the event bus
6. Event bus uses source property to route message to SQS queue
7. Lambda watching SQS queue pull message for processing
8. Lambda uses message detail to decide whether to PUSH, email, sms
9. Owner receives notification(s)

Diagram v2.24.2025

(click to open at actual size)

Source Code

Like Notifications - Diagram Source

cart-add-items.sd

entryspacing 0.7
frame #lightblue Notification System - Likes

participantspacing 2
entryspacing 0.5
bottomparticipants

actor "Customer" as customer #orange
lifelinestyle customer #lightgray:1:solid

participant "API" as api #FB6DEA
lifelinestyle api #lightgray:1:solid

participant "Backend" as backend #lightgrey
lifelinestyle backend #lightgray:1:solid

database "Likes Table" as likes #lightgreen
lifelinestyle likes #lightgray:1:solid

database "Notifications Table" as notes #red
lifelinestyle notes #lightgray:1:solid

participant "Event Bus" as bus #orange
lifelinestyle bus #lightgray:1:solid

participant "Notifications Queue" as notesQ #pink
lifelinestyle notesQ #lightgray:1:solid

participant "Notification Lambda" as noteLambda #lightblue
lifelinestyle noteLambda #lightgray:1:solid

actor "Owner" as owner #lightgrey
lifelinestyle owner #lightgray:1:solid

parallel
customer -> api:Likes Look
<color #grey>Look ID
api ->> backend:Create Like
<color #grey>Look ID
backend ->> likes:INSERT
<color #grey>Look ID, Customer ID</color>
parallel end
likes -->> backend:SUCCESS

backend -> notes:INSERT
<color #grey>Look ID, Customer ID
notes -->> backend:SUCCESS

box over notes:At this point, the Owner would
be able to see the notification in
their list as 'Someone liked
 your look!' with images of the look
and the other user...

backend -> bus:Create Like Message
<color #grey>Notification ID, Recipient ID, Media URLs, Deep Link

box over bus:Bus uses 'Source'
property to route
the message to the
appropriate Queue

bus -->> notesQ:
box over notesQ:Message waits
in queue for
processing

noteLambda <<-- notesQ:Message Pulled From Queue

box over noteLambda:Lambda processes message:
Send Push Notification?
Send Email?
Send SMS?

noteLambda -> owner:PUSH / EMAIL / SMS

rbox over owner: ARRIVED