Systems Architecture & Distributed Systems Topics
Large-scale distributed system design, service architecture, microservices patterns, global distribution strategies, scalability, and fault tolerance at the service/application layer. Covers microservices decomposition, caching strategies, API design, eventual consistency, multi-region systems, and architectural resilience patterns. Excludes storage and database optimization (see Database Engineering & Data Systems), data pipeline infrastructure (see Data Engineering & Analytics Infrastructure), and infrastructure platform design (see Cloud & Infrastructure).
CAP Theorem and Consistency Models
Understand the CAP theorem and how Consistency, Availability, and Partition Tolerance interact in distributed systems. Know different consistency models including strong consistency such as linearizability, eventual consistency, causal consistency, and session consistency, and how to apply them to different use cases. Be familiar with consensus protocols and distributed coordination primitives such as Raft and Paxos, quorum reads and writes, two phase commit and when to use them. Understand trade offs between consistency and availability under network partitions, patterns for hybrid approaches where different data uses different guarantees, and the product and developer experience implications such as latency, stale reads, and API contract clarity.
High Availability and Disaster Recovery
Designing systems to remain available and recoverable in the face of infrastructure failures, outages, and disasters. Candidates should be able to define and reason about Recovery Time Objective and Recovery Point Objective targets and translate service level agreement goals such as 99.9 percent to 99.999 percent into architecture choices. Core topics include redundancy strategies such as N plus one and N plus two, active active and active passive deployment patterns, multi availability zone and multi region topologies, and the trade offs between same region high availability and cross region disaster recovery. Discuss load balancing and traffic shaping, redundant load balancer design, and algorithms such as round robin, least connections, and consistent hashing. Explain failover detection, health checks, automated versus manual failover, convergence and recovery timing, and orchestration of failover and reroute. Cover backup, snapshot, and restore strategies, replication and consistency trade offs for stateful components, leader election and split brain mitigation, runbooks and recovery playbooks, disaster recovery testing and drills, and cost and operational trade offs. Include capacity planning, autoscaling, network redundancy, and considerations for security and infrastructure hardening so that identity, key management, and logging remain available and recoverable. Emphasize monitoring, observability, alerting for availability signals, and validation through chaos engineering and regular failover exercises.
State Management and Data Flow Architecture
Design and reasoning about where and how data is stored, moved, synchronized, and represented across the full application stack and in distributed systems. Topics include data persistence strategies in databases and services, application programming interface shape and schema design to minimize client complexity, validation and security at each layer, pagination and lazy loading patterns, caching strategies and cache invalidation, approaches to asynchronous fetching and loading states, real time updates and synchronization techniques, offline support and conflict resolution, optimistic updates and reconciliation, eventual consistency models, and deciding what data lives on the client versus the server. Coverage also includes separation between user interface state and persistent data state, local component state versus global state stores including lifted state and context patterns, frontend caching strategies, data flow and event propagation patterns, normalization and denormalization trade offs, unidirectional versus bidirectional flow, and operational concerns such as scalability, failure modes, monitoring, testing, and observability. Candidates should be able to reason about trade offs between latency, consistency, complexity, and developer ergonomics and propose monitoring and testing strategies for these systems.
Service Discovery & Configuration Management
Service discovery and configuration management within distributed systems. Covers runtime service lookup patterns (service registries, DNS-based discovery, and Kubernetes service discovery), health checks, load balancing, and centralizing configuration across services. Includes dynamic configuration, feature flags, secret management, versioned configuration, rollout strategies, and related operational concerns such as security, consistency, and observability. Topics span implementations with tools like Consul, Etcd, Zookeeper, as well as cloud-native and IaC approaches for microservices architectures.
Distributed Systems Troubleshooting
Focused on diagnosing incidents specific to distributed architectures and multi service systems. Candidates should be able to detect and analyze network latency packet loss service to service communication failures cascading failures load balancing misconfiguration and data consistency anomalies. The topic covers observability practices such as distributed tracing aggregated metrics and logs correlation identifiers health checks and alerting; instrumentation strategies for cross service request flow mapping; and remediation patterns such as timeouts retries circuit breakers backpressure and resynchronization. Interviewers assess the ability to reason about partitioning and consistency models reproduce issues safely across services and propose mitigation and longer term fixes for distributed failure modes.
Multi Region and Geo Distributed Systems
Designing and operating systems and infrastructure that span multiple geographic regions and cloud or on premise environments. Candidates should cover data placement and replication strategies and trade offs such as synchronous versus asynchronous replication, single primary versus multi master topologies, read replica placement, quorum selection, conflict detection and resolution, and techniques for minimizing replication lag. Discuss consistency models across regions including strong, causal, and eventual consistency, cross region transactions and the trade offs of two phase commit versus compensation patterns or eventual reconciliation. Explain latency optimization and traffic routing strategies including read and write locality, routing users to the nearest region, domain name system based routing, anycast, global load balancers, traffic steering, edge caching and content delivery networks, and deployment techniques such as blue green and canary rollouts across regions. Cover network and interconnect considerations such as direct private links, virtual private network tunnels, internet based links, peering strategies and internet exchange points, bandwidth and latency implications, and how they influence failover and replication choices. Describe availability zones and their role in fault isolation, how to design for high availability within a region using multiple availability zones, and when to use multi region active active or active passive topologies for resilience. Plan for disaster recovery and resilience including failover detection and automation, backup and restore, recovery time objectives and recovery point objectives, cross region failover testing, run books, and operational playbooks. Include security, identity, and compliance concerns such as data residency and sovereignty, regulatory constraints, cross border encryption and key management, identity federation and authorization across regions, and cost and legal implications of region selection. Discuss operational practices including monitoring and alerting for region health and replication metrics, capacity planning, deployment automation, observability, run book procedures, and testing strategies for simulated region failures. Finally reason about workload partitioning and state localization, replication frequency, read and write locality, cost and complexity trade offs, and provide concrete patterns or examples that justify chosen architectures for global user bases.
Load Balancing and Traffic Distribution
Covers why load balancers are used and how traffic is distributed across backend servers to avoid single server bottlenecks, enable horizontal scaling, and provide fault tolerance. Candidates should know common distribution algorithms such as round robin, least connections, weighted balancing, and consistent hashing, and understand trade offs among them. Explain the difference between layer four and layer seven load balancing and the implications for routing, request inspection, and protocol awareness. Discuss stateless design versus stateful services, the impact of session affinity and sticky sessions, and alternatives such as external session stores or token based sessions to preserve scalability. Describe high availability and resilience patterns to mitigate a single point of failure, including active active and active passive configurations, health checks, connection draining, and global routing options such as DNS based and geo aware routing. At senior and staff levels, cover advanced capabilities like request routing based on metadata or headers, weighted traffic shifting for canary and blue green deployments, traffic mirroring, rate limiting and throttling, integration with autoscaling, and strategies for graceful degradation and backpressure. Also include operational concerns such as secure termination of transport layer security, connection pooling, caching and consistent hashing for caches, monitoring and observability, capacity planning, and common debugging and failure modes.
Multi Region Disaster Recovery
Designing systems for resilience and availability across geographic regions, including strategies for cross region replication, failover, and operational recovery. Candidates should understand deployment models such as active active and active passive and the trade offs they imply for availability, consistency, cost, and operational complexity. Discuss replication topologies and the differences between synchronous and asynchronous replication and how those choices affect consistency and the recovery point objective. Cover leader election and failover coordination mechanisms, conflict resolution approaches including last write wins, version vectors, and convergent data types, and implications for transactional guarantees and global transactions. Include global traffic routing and failover techniques such as DNS based routing, global load balancing, health checks, and the impact of routing and time to live on failover behavior. Address data partitioning and cross region latency trade offs, strategies for orchestrating data recovery and region seeding, backup and restore practices, and testing approaches such as planned failovers, rehearsal drills, and chaos testing. Explain how to derive and meet recovery time objective and recovery point objective from business requirements, and consider monitoring, observability, automation, runbooks, cost considerations, and compliance and data residency requirements.
Distributed Systems Security
Security considerations and patterns for distributed systems and multi service environments. Topics include service to service authentication and authorization, key management and secret rotation at scale, implications of eventual consistency for access control decisions, securing inter service communication, distributed logging and auditing, handling security during partial failures and partitioning, Byzantine fault tolerant scenarios and consensus impacts on security, tradeoffs between availability confidentiality and integrity across regions, and designing resilient defenses for systems spanning multiple data centers or organizational boundaries.