High Availability & Disaster Recovery

Grand Central provides enterprise-grade high availability and disaster recovery capabilities designed to ensure business continuity for critical banking operations with minimal downtime and data loss.

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Resilience Overview

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High Availability Architecture

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Multi-Zone Deployment

Availability Zone Strategy deploys services across multiple availability zones within each region to maximize uptime. Each zone operates independently with isolated power, cooling, and networking infrastructure. Container Distribution spreads Kubernetes pods across availability zones using pod anti-affinity rules and zone-aware scheduling. The scheduler automatically redistributes workloads when zones become unavailable, ensuring resource balancing across healthy zones. Data Layer Redundancy replicates databases and storage across zones with synchronous replication for critical data. Zone-redundant storage provides automatic failover without data loss, maintaining strong data consistency guarantees even during zone outages. Network Resilience spans network infrastructure across multiple zones with load balancer distribution, network redundancy, and traffic health monitoring. Automatic rerouting directs traffic away from unhealthy zones without manual intervention. Performance Optimization ensures optimal performance across availability zones through locality-aware routing that preferentially directs traffic to same-zone backends. Cross-zone latency optimization, bandwidth management, and cache distribution minimize performance impact of multi-zone deployment.

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Load Balancing & Auto-Scaling

Intelligent Traffic Distribution provides advanced load balancing with health monitoring and automatic scaling capabilities to handle varying traffic patterns. Layer 4 Load Balancing operates at the network layer, providing TCP/UDP load balancing with connection-based routing. High throughput handling and low latency processing make this ideal for high-volume, low-latency scenarios. Layer 7 Load Balancing operates at the application layer, enabling HTTP/HTTPS load balancing with content-based routing. SSL termination offloads encryption overhead, and session affinity maintains user session consistency. Readiness Probes determine when pods are ready to receive traffic by checking application endpoints before routing requests. Pods failing readiness checks are automatically removed from load balancer pools. Liveness Probes monitor application health and restart unhealthy containers automatically. Kubernetes restarts pods that fail liveness checks, replacing failed instances without manual intervention. Startup Probes handle slow-starting containers during initialization, allowing extended startup time before applying normal health check timeouts. Horizontal Pod Autoscaler scales pod count based on CPU utilization, memory usage, custom metrics, or predictive models. Scaling decisions occur within seconds of threshold breaches, adding or removing pods to match demand. Vertical Pod Autoscaler provides resource recommendations and automatic resource adjustments for right-sizing optimization. Cost optimization occurs by preventing over-provisioning while ensuring adequate resources.

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Circuit Breaker & Failover

Fault Tolerance Patterns implement automated failure detection and recovery mechanisms to prevent cascade failures across the system. Circuit Breaker Implementation prevents cascade failures by detecting and isolating failing services. The circuit breaker operates in three states: CLOSED (normal operation with requests flowing through), OPEN (failure detected with requests immediately failing), and HALF-OPEN (testing recovery with limited requests allowed). Exponential Backoff Retry implements jittered retry delays that increase exponentially with each failure. Fixed delay retry provides consistent retry intervals for specific scenarios, with circuit breaker integration preventing retry storms. Retry Policies configure maximum retry attempts, timeout values, retryable error codes, and dead letter queue routing for permanently failed requests. Fallback Services provide alternative service implementations for critical functions when primary services fail. Cached responses serve stale but valid data when primary services are unavailable. Feature Flags dynamically disable non-essential features during incidents, reducing system load and isolating problems. Queue management temporarily buffers requests for delayed processing when backends are overwhelmed.

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Disaster Recovery Strategy

Cross-Region Replication provides ultimate resilience through geographic redundancy. Data and services replicate across multiple Azure regions to ensure business continuity during regional failures. Data Replication Patterns support both synchronous and asynchronous strategies: Region Selection Criteria balances technical factors (network latency, available Azure services, compliance requirements, disaster risk correlation) with business factors (customer distribution, regulatory requirements, cost optimization, support coverage). Backup & Restore implements a comprehensive multi-layered backup approach with automated restoration capabilities. Backup Types & Schedules operate on three tiers: Backup Storage & Security utilizes geo-redundant storage with cross-region replication, immutable backup storage, and long-term retention tiers. Security controls include encryption at rest, access control policies, backup integrity verification, and comprehensive audit trail logging. Restore Procedures provide both automated and full system restore capabilities: Failover Procedures implement intelligent failover orchestration with coordination between automated systems and operational teams. Failover Triggers activate disaster recovery procedures based on four categories. Critical failures include complete region outages, database corruption, security breaches, and catastrophic infrastructure failures requiring immediate response. Performance degradation triggers monitor response time thresholds, error rate spikes, resource exhaustion, and SLA breach conditions that impact service quality. Planned maintenance enables controlled failover during scheduled updates, infrastructure upgrades, security patches, and capacity expansion activities. Manual initiation supports administrative decisions, testing procedures, compliance requirements, and business continuity drills. Failover Process Flow executes through coordinated phases. Failure detection uses automated monitoring to identify critical issues requiring intervention. Impact assessment evaluates the scope of the failure and determines the appropriate recovery strategy. Traffic redirection updates DNS and load balancer configurations to route traffic to recovery infrastructure. Service validation performs comprehensive health checks and service readiness verification to ensure recovered services are fully operational. Failback Procedures ensure safe return to the primary region through two phases. Preparation phase validates primary region health, verifies data synchronization, conducts security assessments, and performs performance testing before initiating return. Execution phase implements gradual traffic shift using blue-green deployment patterns, maintains continuous monitoring and validation throughout the transition, and preserves rollback capability if issues emerge during the process. Recovery Testing implements continuous validation of disaster recovery procedures and capabilities through regular testing schedules and methodologies. Testing Schedule & Types operate on multiple levels with increasing scope. Component testing runs regularly and focuses on individual system elements including database failover, load balancer switching, backup validation, and service health checks. Partial DR testing validates larger system segments through service layer failover, data replication testing, network failover, and application recovery procedures. Full DR testing occurs bi-annually (every 6 months) and exercises complete region failover with end-to-end validation, business process testing, and stakeholder involvement to ensure readiness for major events. Chaos Engineering uses controlled failure injection to test system resilience through two approaches. Infrastructure chaos targets the platform layer with pod termination, network partitioning, resource exhaustion, and disk failures to verify infrastructure resilience. Application chaos focuses on service behavior through simulated service unavailability, latency injection, error rate increases, and configuration corruption to validate application-level fault handling. Game Days coordinate disaster scenarios with cross-team participation to test both technical capabilities and organizational readiness. Scenario types include regional outages, security incidents, data corruption events, and third-party failures that simulate realistic crisis conditions. Objectives focus on team coordination, communication protocols, decision-making processes, and continuous learning and improvement from each exercise. Success Metrics & KPIs define recovery targets and operational excellence. Recovery Time Objective (RTO) commitment is 6 hours for nominal situations, with best-effort recovery during region unavailability. Recovery Point Objective (RPO) varies by data criticality, with critical financial data using synchronous replication for minimal data loss. Availability targets are tier-dependent as defined in service level agreements. Test success metrics ensure disaster recovery procedures remain effective and teams stay prepared.

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Business Continuity Features

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Compliance & Governance

Service Level Agreements establish a comprehensive framework with measurable commitments structured across three service tiers. Signature Tier provides 99.9% uptime SLA, delivering the highest level of availability for mission-critical banking operations requiring maximum resilience. Premium Tier provides 99.5% uptime SLA with comprehensive disaster recovery capabilities, offering strong availability commitments suitable for production banking services. Essential Tier provides 99.5% uptime SLA, delivering foundational availability guarantees with standard disaster recovery procedures. Recovery Commitments: All tiers operate with a 6-hour Recovery Time Objective (RTO) for nominal situations. During regional outages, recovery is provided on a best-effort basis. Recovery Point Objective (RPO) varies by data type, with critical financial data utilizing synchronous replication for minimal data loss. Regulatory Compliance ensures adherence to banking regulations and international standards for business continuity. Banking regulations include Basel III operational resilience requirements, PCI DSS availability standards, SOX internal controls for financial reporting continuity, and regional banking standards specific to operating jurisdictions. Industry standards encompass ISO 22301 business continuity management, ISO 27031 ICT readiness for business continuity, NIST cybersecurity framework resilience objectives, and COBIT governance framework for IT service continuity.

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Best Practices

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Next Steps