Real time updates

WebSocket
Server Sent Event
WebSockets vs SSE vs API polling

Long running tasks

Message queues

Data contention

Database ACID

Scaling reads

Caching
Database Replication and read replicas

Scaling writes

Database Sharding

Handling large blobs

Pre-signed urls

Multi step process

Saga choreography vs saga orchestration

Proximity based services

Something something geolocalisation
Postgres has extensions for this