Tilt by Amo

What is Tilt

Tilt is video creation app(same as beReal), the app activates your phone's front and back cameras at the same time
User can select any stream (front or back) as major stream and other will be shown as smaller screen with major.

Requirements (CRUD)

Functional

1. User can create Account on Tilt

2. Whenever new video is posted by friend, user get Push notification

3. Update self profile

4. User can add friends

5. (POST) User can create dualmode video & save on cloud

6. Delete friend

7. Delete account

Non-Functional

1. Highly available

2. Secure. Videos should not be leaked on internet

BOE

Metric	Description
QPS(Queries per second)	Very low, as in when someone opens app then request is sent to system and system sends the updates
BW Estimates
Storage Requirements	DAU = 1 Million. 1 user uploads 2 videos/day. Video duration = 10 min(100MB) Total video uploads = 1M x 2 = 2M. Data = 2M x 100MB = 200 TB /day. For 5 years = 200TB x 365 x 5 = 365 x 10¹⁵ bytes

API Design (CRUD)

REST API?
REST API Versioning(v1,v2)

1. User can create Account on tilt	2. User reads timeline whenever he opens the app	3. Update self profile	5. User can create dualmode video & save on cloud	5. Delete Account
`curl -X POST -H "Content-Type: application/json" -d '{"name": "user_id"}' http://127.0.0.1:8080/v1/create_account -vvv`	`curl -X GET http://127.0.0.1:8080/v1/get_all_data`	`curl -X PUT -H "Content-Type: application/json" -d '{ "user_id": "current_user_id", "new_name": ["new_name"] }' http://127.0.0.1:8080/v1/update -vvv`	User saves video in device library Directly send video to tilt server (in parts) `curl -X POST -H "Content-Type: application/json" http://127.0.0.1:8080/v1/upload_video -d '{ "user_id": "id1", "fragment_no": "fragement-n" }'`	`curl -X DELETE -H "Content-Type: application/json" http://127.0.0.1:8080/v1/delete_account -d '{ "user_id": "id1", }'`
`// Create account //url=toilt.amo.com POST https://url/v1/create_account header { Authorization: {Bearer "API_KEY_TOKEN"}, /Mandatory added by HTTP Start/ Content-len: 0 Host: //Calculated when req is sent UserAgent: Postman Accept: / Accept-Encoding: gzip, deflate, br Connection: Keepalive /Mandatory added by HTTP End/ } body { //JSON "user_name": "" }`	`GET https://url/v1/get_location header { Authorization: {Bearer "API_KEY_TOKEN"}, ..other fields.. } body { //JSON "my_username": "", }`	`PUT http://url/v1/update header { Authorization: {Bearer "API_KEY_TOKEN"}, ..other fields.. } body { //JSON "userid": "", "new_name": "", }`	`PUT http://url/v1/upload header { Authorization: {Bearer "API_KEY_TOKEN"}, ..other fields.. } body { //JSON "user_id": "", "fragment_no": "1" }`	`DELETE http://url/v1/delete_account header { Authorization: {Bearer "API_KEY_TOKEN"}, ..other fields.. } body { //JSON "my_username": "" }`

1. User can create Account on tilt

2. User reads timeline whenever he opens the app

3. Update self profile

5. User can create dualmode video & save on cloud

5. Delete Account


curl -X POST -H "Content-Type: application/json" 
-d '{"name": "user_id"}' 
http://127.0.0.1:8080/v1/create_account -vvv


curl -X GET http://127.0.0.1:8080/v1/get_all_data


curl -X PUT -H "Content-Type: application/json" -d 
'{
  "user_id": "current_user_id", 
  "new_name": ["new_name"]
}' 
http://127.0.0.1:8080/v1/update -vvv

User saves video in device library
Directly send video to tilt server (in parts)


curl -X POST -H "Content-Type: application/json" 
http://127.0.0.1:8080/v1/upload_video
-d '{
  "user_id": "id1",
  "fragment_no": "fragement-n"
}'


curl -X DELETE -H "Content-Type: application/json" 
http://127.0.0.1:8080/v1/delete_account
-d '{
  "user_id": "id1",
}'


// Create account
//url=toilt.amo.com
POST https://url/v1/create_account 
header {
  Authorization: {Bearer "API_KEY_TOKEN"},

  /*Mandatory added by HTTP Start*/
  Content-len: 0                        
  Host:        //Calculated when req is sent
  UserAgent: Postman
  Accept: */*       
  Accept-Encoding: gzip, deflate, br
  Connection: Keepalive
  /*Mandatory added by HTTP End*/
}
body {  //JSON
  "user_name": ""
}

  
GET https://url/v1/get_location
header {
  Authorization: {Bearer "API_KEY_TOKEN"},
  ..other fields..
}
body {  //JSON
  "my_username": "",
}

  
PUT http://url/v1/update
header {
  Authorization: {Bearer "API_KEY_TOKEN"},
  ..other fields..
}
body {  //JSON
  "userid": "", 
  "new_name": "",
}

    
PUT http://url/v1/upload
header {
  Authorization: {Bearer "API_KEY_TOKEN"},
  ..other fields..
}
body {  //JSON
  "user_id": "",
  "fragment_no": "1"
}

  
DELETE http://url/v1/delete_account
header {
  Authorization: {Bearer "API_KEY_TOKEN"},
  ..other fields..
}
body {  //JSON
  "my_username": ""
}

DB Schema

Graph DB


// user Table
| userid (pk) | username | creation_timestamp | last_seen |

// password table
| userid (pk) | username | password_hash | password_creation_date | expiry_time |

Friends, friends of friends, Likes, comments, videos relationship Would be stored on Graph DB
Videos, Comments: Stored on seperate Object store
Coments:

HLD

User uploading video, Friend is notified and Friend watches video

            @startuml
            actor user as u
            box datacenter
            participant "Load\nBalancer" as lb
            participant "App\nServer" as as
            database graphDB as gdb
            database userDB as udb
            database "ObjectStore\nAWS S3" as ostore   #LightPink
            participant "Notification\nSender" as ns
            end box
            participant CDN as cdn
            actor friend_f1 as f
            
            note over u
            Create video
            end note
            
            note over udb
            Note last_seen
            time of user
            We will not send
            notification to 
            user not active
            in last 7 days
            end note
            
            u -> lb: HTTP POST video
            lb -> as: HTTP POST video
            group Storing video on Object store
            as -> ostore: Store Video on Object Store
            ostore -> as: video URL
            as -> gdb: Create video node(url)
            end
            
            as -> ns: user_id=uid1\nuploaded video\nObject store
            ns -> gdb: Get all\nfriends of uid1
            gdb -> ns: f1,f2
            group Send notification to user active in last 7 days
            ns -> udb: Is friend active\nin last 7 days
            udb -> ns: Yes f1
            ns -> cdn: video
            ns -> f: Notification\nUser1 has new\nVideo
            end
            
            group Friend Checks Video of uid1
            note over f
            click to
            check video
            end note
            f -> ns: HTTP GET Video
            ns -> cdn: video
            note over cdn
            Video is
            cached
            end note
            cdn -> f: video
            end
            
            note over cdn
            Video is cached
            with deletion
            policy. if not
            read for 10 days
            delete
            end note
            
            @enduml

Storing videos on CDN:
All videos are not stored directly on CDN
As user uploads a new video its stored on object store (e.g., AWS S3, Azure Blob Storage)
CDN caches content only when requested by users.
Videos are stored with proper lifecycle policies (e.g., auto-deletion after a period for inactive videos).

Adaptive Caching Strategy on CDN:
- Only store videos on the CDN when they cross a popularity threshold (e.g., number of views, likes, or shares).
- Prioritize celebrity or influencer content for CDN storage due to higher demand
- Implement a Least Recently Used (LRU) cache eviction strategy on the CDN to optimize storage costs.