This document discusses designing an offline-online sync system. It explores using databases with built-in sync support like Couchbase and PouchDB. Database replication is also considered but has issues like security, conflicts, and business logic handling. Browser-based solutions have limitations from storage and performance. The plan is to identify needed offline features, follow a git-style pull-push model, and leverage cloud infrastructure and messaging queues. Code examples show using a database, queue, and triggering sync from the local machine to cloud components.

1. Designing
offline online sync system
How to design and implement a (partial) offline–online sync system

2. Why we need offline support?
Connection is bound to fail, sometimes

3. Common Ideas
• Database : built-in support
• Couchbase
• PouchDB
• Firestore
• Cloud vendors
• Database replication
• Handle the replication by managing master and slave model
• Database is inside of the browser
• Use local-storage and PWA

4. Problems
• CouchDB is not traditional database, so hard to use it in traditional
business scenarios
• Same issue goes with any other built-in sync supported databases
• Database replication has
• Security issue
• Conflict issue
• Business logic handling issue
• Browser based system
• Not possible if the dropdowns have too many items.
• Browser has storage limitation.
• SQLite can be shared with anyone
• New browser needs to load all required data
• Background processing in the browser can hamper performance

5. Plan
• Try to find which features are actually needed in offline
• Sale entry
• Follow the git style
• Pull
• Then push
• Try to leverage the infrastructure and user base
• Azure cloud messaging (Queue)
• Visit outlets and setup necessary software. Teach the user to run the
command

6. Code
Database
Queue
Code
Database
Queue
Client
Timer
service
Local machine in a branch
Cloud components
Trigger

7. Azure
Cloud
Branch 1
Branch 2
Branch 3
Branch 4
Branch 5
Branch 6

8. Codes
Pseudo demo

9. Find me
• Facebook: https://www.facebook.com/foyzulsacademy
• Blog: https://dev.to/foyzulkarim
• Twitter: https://twitter.com/foyzul_karim
• GitHub: https://github.com/foyzulkarim
• LinkedIn: https://www.linkedin.com/in/foyzul
• Email: foyzulkarim@gmail.com