Hybrid Cloud Architecture: Balancing On-Premises and Cloud for Mid-Size Businesses

# Hybrid Cloud Architecture: Balancing On-Premises and Cloud for Mid-Size Businesses

Not everything belongs in the cloud, and not everything belongs on-premises. Hybrid cloud—running some workloads locally and others in AWS, Azure, or Google Cloud—is the pragmatic architecture most mid-size businesses converge on. The challenge is making good placement decisions.

## When Hybrid Cloud Makes Sense

Hybrid cloud is the right choice when:

• **Some workloads need low latency** — Manufacturing control, real-time video processing, or applications that perform poorly over WAN
• **Compliance requires data locality** — Certain industries or contracts require data to remain on-premises or in specific geographic regions
• **Legacy applications cannot migrate** — Older applications tightly coupled to on-premises infrastructure are expensive to refactor
• **Cloud costs exceed on-prem for specific workloads** — 24/7 high-compute workloads can be cheaper on owned hardware
• **You need burst capacity** — Baseline workloads run on-prem with cloud handling demand spikes

## Workload Placement Decision Framework

### Cloud-First Workloads Put these in cloud unless you have a specific reason not to:

| Workload | Why Cloud | |----------|----------| | Email and collaboration (M365, Google Workspace) | Already cloud-native, better user experience | | CRM and SaaS applications | Vendor-managed, scalable, always current | | Development and testing | Spin up/down on demand, pay only for usage | | Disaster recovery | More cost-effective than maintaining a physical DR site | | Web applications and APIs | Scalable hosting with global CDN |

### On-Premises Workloads Keep these local when the business case supports it:

| Workload | Why On-Prem | |----------|------------| | Legacy line-of-business apps | Migration cost exceeds benefit | | High-frequency database transactions | Latency-sensitive, predictable load | | Large file storage with local access needs | WAN bandwidth bottleneck | | Manufacturing and IoT control | Real-time, safety-critical | | Regulatory-restricted data | Compliance requires physical control |

## Architecture Patterns

### Pattern 1: Cloud for SaaS + On-Prem for Infrastructure

Most common for businesses starting their cloud journey: - Cloud: Email, CRM, collaboration, web presence - On-prem: File servers, Active Directory, line-of-business applications, databases - Connection: Site-to-site VPN or ExpressRoute/Direct Connect

### Pattern 2: Cloud for DR + On-Prem for Production

Production runs on-premises with cloud-based disaster recovery: - Primary workloads on local servers and storage - Cloud receives backup replicas for DR failover - RTO of hours instead of days (compared to tape/offsite backup) - Cost-effective: cloud DR resources only run during actual disasters

### Pattern 3: Cloud for Scale + On-Prem for Baseline

Baseline load runs on-premises; cloud handles peaks: - Predictable workloads on owned hardware (lower TCO for steady-state) - Cloud auto-scales for seasonal demand, batch processing, or special events - Requires application architecture that supports horizontal scaling

## Connectivity Requirements

Hybrid cloud depends on reliable, fast connectivity between on-premises and cloud:

### Site-to-Site VPN - Encrypted tunnel over public internet - Cost: included with most firewalls ($0 additional) - Performance: limited by internet bandwidth and latency - Best for: light cloud usage, DR replication, small data volumes

### Dedicated Connection (ExpressRoute / Direct Connect) - Private connection to cloud provider, bypasses public internet - Cost: $200-$2,000+/month depending on bandwidth - Performance: predictable latency, guaranteed bandwidth - Best for: large data volumes, latency-sensitive applications, heavy cloud usage

### SD-WAN - Software-defined WAN optimizes traffic across multiple connections - Can intelligently route cloud traffic vs on-prem traffic - Provides redundancy and failover between connections - Best for: multi-site businesses with mixed cloud and on-prem workloads

## Identity Integration

The biggest technical challenge in hybrid cloud is identity:

• **Azure AD Connect / Entra Connect** — Synchronize on-premises Active Directory with cloud identity
• **Single Sign-On (SSO)** — Users authenticate once for both on-prem and cloud resources
• **Conditional access** — Enforce security policies consistently across both environments
• **Password hash sync or federation** — Choose the right auth model for your compliance requirements

## Cost Management

Hybrid cloud cost pitfalls:

• **Data egress charges** — Moving data out of cloud is expensive. Architect to minimize egress
• **Duplicate infrastructure** — Running the same workload in both places doubles the cost
• **Idle cloud resources** — On-prem servers waste electricity when idle; cloud wastes money
• **Overlooking on-prem costs** — Include power, cooling, facilities, and labor in TCO comparisons

## Getting Started

Summit DNC designs and manages hybrid cloud architectures for businesses across Southern California. We help you make smart placement decisions, implement secure connectivity, and manage both environments as one unified infrastructure.