Cloud Computingとは何ですか？

Before cloud computing, businesses that needed servers had to purchase physical hardware, install it in a data center or server room, configure it, and maintain it indefinitely. This model required large upfront capital expenditure, significant IT operations overhead, and resulted in either over-provisioning (paying for capacity you don't use) or under-provisioning (unable to handle traffic spikes). Cloud computing replaced this with on-demand infrastructure available by the minute, with costs that scale directly with usage.

Cloud services are organized into three primary delivery models. Infrastructure as a Service (IaaS) provides raw compute, storage, and networking — you manage the operating system, middleware, and applications (examples: AWS EC2, Google Compute Engine). Platform as a Service (PaaS) provides a complete managed environment where you deploy your application code without managing the underlying servers (examples: Heroku, Google App Engine, AWS Elastic Beanstalk). Software as a Service (SaaS) is fully managed applications delivered over the internet (Salesforce, Gmail, Slack). Most businesses use a mix of all three.

The major cloud providers — Amazon Web Services (AWS), Microsoft Azure, and Google Cloud Platform (GCP) — each offer hundreds of services: managed databases, machine learning APIs, CDNs, message queues, data warehouses, identity management, and more. Choosing the right services, architecting systems for cost efficiency, and managing cloud spend (which can balloon dramatically without governance) requires genuine expertise. Cloud cost optimization has become its own discipline as businesses discover that naively migrating to the cloud can actually increase costs.