Lag Function: Access data in a previous row in the same result set without having to join the table to itself.
How to use the SQL LAG window function to compare current and previous row values, with practical query and table output.
Postgres
System Design: Build a Database Cluster with Primary(Master) & Read Replica(Slave)
Create a DB Cluster which ensures high availability & fast responses with the use of a read Replica. Use Docker & Postgres to create a local database cluster where 1 DB is a master which we write to and 1 DB is a replica which copies data for higher availability & resiliency.