Backend Engineering & Performance Topics
Backend system optimization, performance tuning, memory management, and engineering proficiency. Covers system-level performance, remote support tools, and infrastructure optimization.
Scalability Analysis and Bottleneck Identification
Techniques for analyzing existing systems to find and prioritize bottlenecks and to validate scaling hypotheses. Topics include profiling and benchmarking strategies instrumentation and monitoring of latency throughput error rates and resource utilization; identification of common bottlenecks such as database write throughput central processing unit saturation memory pressure disk input output limits and network bandwidth constraints; designing experiments and load tests to reproduce issues and validate mitigations; proposing incremental fixes such as caching partitioning asynchronous processing or connection pooling; and measuring impact with clear metrics and iteration. Interviewers will probe the candidate on moving from observations to root cause and on designing low risk experiments to validate improvements.
Quantified backend system contributions
Prepare 3-4 specific examples of backend systems you've architected or significantly improved. For each, quantify the impact: scalability improvements (e.g., 'handled 10x traffic growth'), performance wins (e.g., 'reduced p99 latency from 500ms to 50ms'), reliability improvements (e.g., 'achieved 99.99% uptime'), or business impact (e.g., 'unblocked 3 product teams'). Be ready to briefly describe the technical challenge and your role.
Performance Optimization and Latency Engineering
Covers systematic approaches to measuring and improving system performance and latency at architecture and code levels. Topics include profiling and tracing to find where time is actually spent, forming and testing hypotheses, optimizing critical paths, and validating improvements with measurable metrics. Candidates should be able to distinguish central processing unit bound work from input output bound work, analyze latency versus throughput trade offs, evaluate where caching and content delivery networks help or hurt, recognize database and network constraints, and propose strategies such as query optimization, asynchronous processing patterns, resource pooling, and load balancing. Also includes performance testing methodologies, reasoning about trade offs and risks, and describing end to end optimisation projects and their business impact.
Caching Strategies and In Memory Storage
Understanding caching mechanisms (HTTP caching, application-level caching with Redis/Memcached). Cache invalidation strategies, TTL, and when to cache. Performance implications.
System Resource and Input Output Optimization
Techniques for managing system resources and optimizing input output including memory management, buffer and cache tuning, storage tiering and device selection, disk access patterns and throughput trade offs, central processing unit utilization, contention resolution, and diagnosing resource bottlenecks. Candidates should discuss monitoring and observability, trade offs between latency and throughput, caching strategies, memory pooling and fragmentation mitigation, and platform specific constraints when optimizing resource usage.
Caching and Performance Optimization
Covers design and implementation of multi layer caching and end to end performance strategies for web and backend systems. Topics include client side techniques such as browser caching, service worker strategies, code splitting, and lazy loading for components images and data; edge and distribution techniques such as content delivery network design and caching of static assets; and server side and data layer caching using in memory stores such as Redis and Memcached, query result caching, and database caching patterns. Includes cache invalidation and coherence strategies such as time to live, least recently used eviction, cache aside, write through and write behind, and prevention of cache stampedes. Covers when to introduce caching and when not to, performance and consistency trade offs, connection pooling, monitoring and metrics, establishing performance budgets, and operational considerations such as cache warm up and invalidation during deploys. Also addresses higher level concerns including search engine optimization implications and server side rendering trade offs, and how performance decisions map to user experience and business metrics at senior levels.
Mobile Performance and Energy Optimization
Comprehensive engineering and operational practices for diagnosing, profiling, and optimizing mobile application performance and device energy consumption at feature and system scale. Candidates should be able to explain strategies to reduce application startup time, minimize main thread work to keep the user interface responsive, and stabilize rendering at target frames per second such as sixty frames per second and one hundred and twenty frames per second to avoid application not responding situations. Core topics include memory management and leak prevention, allocation analysis, preventing crashes and responsiveness regressions, efficient rendering of large feeds, complex gesture and input handling, and efficient handling of large media such as photos and video. Common techniques include lazy loading, request batching, image resizing and compression, caching and batching strategies, offline first synchronization, and efficient background processing and scheduling to limit energy impact. Energy and battery focused optimizations include minimizing sensor usage and location service use when unnecessary, geofencing best practices, network and radio optimizations to reduce radio wake ups, preferring push driven updates over polling where appropriate, and designing background tasks to be energy aware. Candidates should demonstrate familiarity with profiling and instrumentation tools and workflows for mobile platforms, interpreting profiler output to identify central processing unit and memory bottlenecks, measuring and quantifying latency and energy impact, designing architectural and code changes to prevent regressions, reasoning about trade offs between native and cross platform implementations, and defining user perceived performance and energy metrics with continuous monitoring and tests to quantify improvements.
Systems and Graphics Optimization Techniques
Covers practical optimization techniques commonly used in systems engineering and real time graphics. Topics include object pooling, level of detail systems, frustum culling, spatial partitioning structures such as quadtrees and octrees, batching and texture atlasing, reducing shader complexity and when to use shaders instead of scripted effects, GPU instancing, texture compression strategies, and memory optimization. Emphasizes trade offs between micro optimization and architectural change, profiling to find hotspots, and understanding the law of diminishing returns when applying optimization effort.
Performance Engineering and Cost Optimization
Engineering practices and trade offs for meeting performance objectives while controlling operational cost. Topics include setting latency and throughput targets and latency budgets; benchmarking profiling and tuning across application database and infrastructure layers; memory compute serialization and batching optimizations; asynchronous processing and workload shaping; capacity estimation and right sizing for compute and storage to reduce cost; understanding cost drivers in cloud environments including network egress and storage tiering; trade offs between real time and batch processing; and monitoring to detect and prevent performance regressions. Candidates should describe measurement driven approaches to optimization and be able to justify trade offs between cost complexity and user experience.