Hybrid Cloud

Hybrid cloud combines public cloud services with on-premises infrastructure or a private cloud, with integration between the environments. Applications, data flows, identity systems, or operational processes connect these environments to support business requirements. Simply owning a data center and separately using a cloud service does not explain the hybrid architecture; the important question is how those environments work together.

For deployment-model exam questions, distinguish hybrid from cloud and on-premises deployments. A cloud deployment runs the relevant workloads in the cloud rather than depending on an on-premises application environment. An on-premises deployment runs workloads in an organization's own or controlled facilities. A hybrid deployment connects these approaches, such as a cloud-hosted application that accesses an on-premises database. An on-premises environment does not need to implement a full private cloud for this common hybrid pattern.

Consider a manufacturer whose factory applications must respond quickly to local machinery. It can retain production control systems on-site while sending selected telemetry to cloud storage and analytics services. Another organization might retain a legacy transaction system in its data center while hosting a customer-facing web application in the cloud. Hybrid architecture also supports phased migration, during which migrated applications must communicate with systems that have not yet moved.

Connectivity is a foundation, but it is not the entire architecture. Engineers must plan IP address ranges, routing, DNS resolution, firewall rules, authentication, and authorization across both environments. Encrypted site-to-site VPN tunnels or dedicated network connections can provide connectivity. A dedicated connection does not automatically provide encryption, and neither connection type eliminates the need to design for failures or control application access.

Application placement should follow dependency and data-flow analysis. Frequent database calls across a wide-area connection can increase response times even when bandwidth is sufficient. Moving large datasets can incur transfer charges and take substantial time. Caching, asynchronous messaging, and keeping tightly coupled application components together can reduce these problems, but each approach introduces its own consistency and operational considerations.

Hybrid cloud offers placement flexibility and can preserve useful infrastructure investments, but it also requires operating two environments. Teams must coordinate monitoring, patching, inventory, security policies, backups, and incident response. Availability depends on the complete application path: a cloud application that requires an on-premises database can become unavailable when the connection or database fails. Redundant connectivity, tested recovery procedures, and clearly defined recovery objectives are therefore important.

Hybrid cloud is not the same as multicloud, which means using services from multiple cloud providers; an architecture can be both. It also does not guarantee lower cost, regulatory compliance, seamless workload portability, or automatic cloud bursting. For exam scenarios, references to retaining local systems while integrating them with cloud resources are strong indicators of hybrid deployment. The defining feature is the connected deployment model, not a particular service or networking product.