Business continuity and disaster recovery (BCDR) in the cloud can be approached from several architectural perspectives, moving beyond the traditional on-premises model of mirroring a primary data center. These modern strategies leverage the cloud's inherent flexibility, global reach, and automation capabilities to create more resilient, cost-effective, and scalable recovery solutions. 

1. Multi-cloud and hybrid-cloud resilience

Instead of relying on a single cloud provider, a multi-cloud or hybrid-cloud strategy is used to minimize a single point of failure and avoid vendor lock-in. This approach can take several forms: 

• Active-active multi-cloud: In this high-cost but low-risk approach, critical applications are distributed and run simultaneously across multiple clouds and regions. Traffic is balanced between all sites, so if one fails, the remaining sites simply absorb the traffic with no downtime.
• Hybrid cloud failover: For businesses with on-premises data centers, a hybrid approach extends the infrastructure to the cloud. The cloud can serve as the secondary disaster recovery site, where a cloud-based replica of an on-premises environment is activated only during a disaster.
• Cloud-to-cloud recovery: If an organization is already all-in on the cloud, they can use one cloud provider for production and a different, secondary provider for their disaster recovery plan. This further mitigates the risk of a regional outage affecting all assets. 

2. Cloud-native disaster recovery strategies

Modern applications built on cloud-native technologies like microservices and containers require specialized BCDR strategies that focus on orchestrating recovery processes rather than restoring entire virtual machines. 

• Automated orchestration: Cloud-native DR is defined by automation, which uses tools and scripts to restore services automatically instead of relying on manual failover. This is crucial for complex, distributed applications and can dramatically reduce Recovery Time Objectives (RTOs).
• Immutable infrastructure: This concept treats cloud infrastructure as temporary rather than permanent. In the event of a disaster, instead of trying to repair the failed infrastructure, it is simply replaced with new, pristine infrastructure, which is a faster and more reliable recovery method.
• Event-driven failover: By using serverless and event-driven architecture, a failover process can be automatically triggered by specific metrics, like health checks, without manual intervention. This provides high reliability and minimizes the impact on production workloads. 

3. As-a-service models for managed BCDR

The emergence of Disaster Recovery as a Service (DRaaS) allows organizations to outsource their BCDR planning and execution to a managed service provider. This makes robust disaster recovery accessible to a wider range of businesses. 

• Managed DRaaS: In this model, a third party takes on all responsibility for designing, testing, and managing the disaster recovery plan. This is ideal for organizations that lack in-house expertise or time to manage their own plan.
• Self-service DRaaS: In this less expensive model, the service provider offers the tools, and the customer is responsible for planning, testing, and managing their own disaster recovery.
• Backup as a Service (BaaS): While not a full DR solution, BaaS is a foundational element that involves backing up data to the cloud. It is often combined with other DR tools to ensure business continuity. 

4. Advanced resilience engineering techniques

To push reliability even further, some organizations utilize advanced techniques inspired by Site Reliability Engineering (SRE) and chaos engineering.

• Chaos engineering: This practice involves intentionally injecting failures into a system to test its resilience under real-world conditions. By simulating regional outages or network partitions, organizations can proactively identify and fix weaknesses in their BCDR plans.
• Fault tolerance as a service: Cloud providers and third-party vendors offer sophisticated tools that enable transparent fault tolerance at the virtual machine level. These mechanisms can include replication, automated failure detection, and recovery to ensure continuous service.
• Global data replication: For applications with a global user base, multi-region database services automatically replicate data across geographically diverse regions. This ensures that even a regional disaster doesn't compromise data integrity or availability.