A classic foundational diagram (and personal favourite): IaaS vs. PaaS vs. SaaS.

These three terms differentiate the layers of the cloud computing stack, all provided “as-a-service”.

Infrastructure-as-a-service: (IaaS)

• The foundation
• Typically targeted at IT administrators / infrastructure and network architects
• A small group of elite vendors
• Examples: AWS (EC2), Microsoft Azure, Google Compute Engine

Platform-as-a-service (PaaS):

• The building blocks
• Typically targeted at app developers
• Vendors are a few key cloud platforms
• Examples: Heroku, AWS Elastic Beanstalk, Google App Engine

Software-as-a-service (SaaS):

• Closest to the consumer
• Typically targeted at end-users
• The most crowded space with thousands of applications deployed in the cloud
• Examples: Gmail, Salesforce CRM, Office 365

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