Constraints in the forms of Triangles, Squares …

Life is full of constraints. It seems like you can never simply "have your cake and eat it".

In Product Development, we have the following Project Triangle:

• Good - quality of the delivered product
• Fast – time taken to deliver the product
• Cheap – cost of designing/ developing/ delivering the final product

We are told to pick any two!

In System Development, the Project Management Triangle follows:

• Scope – the set of functionality for the system or the work to be performed
• Schedule – time taken to complete the project
• Cost – cost of implementing/ delivering the final system

We are told to pick any two!

A variant in System Development, a Project Management Triangle (more like a Square) follows:

• Scope – the set of functionality for the system
• Schedule – time taken to complete the project
• Cost – cost of implementing/ delivering the final system
• Performance – the ability of the system to take load and be responsive

We are told to pick any three!

For distributed systems using shared data among nodes, a similar triangle – known as CAP theorem or Brewer’s Conjecture – exists. The three constraints are:

• Consistency – all distributed nodes are in-sync and consistent and “sees” the same data
• Availability – every client’s request will receive a response, whether successful or not
• Partition tolerance – system continues to operate despite
  • arbitrary messages between nodes dropping or arriving late; or
  • nodes becoming unavailable (due to crashes)

We are told to pick any two!