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System Design cheat sheet & developer notes

System Design cheat sheet and 2 curated developer notes — core concepts, patterns, and interview prep. Maintained by the DevRecall team.

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01 · System Design

Scalability & Architecture

Scalability & Architecture. Scalability Patterns. Horizontal scaling — add more servers; requires stateless app (store sessions in Redis, not in-process). Load balancing — distribute traffic (round-robin, least-connectio…

02 · System Design

Reliability & Interview Framework

Reliability & Interview Framework. Reliability Patterns. Circuit Breaker — stop calling a failing service after N failures; half-open state to probe recovery. Retry with backoff — retry transient failures with exponentia…

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Interview Questions

TypeScript Interview Questions. Comprehensive TypeScript interview questions covering type system, generics, utility types, and best practices:. Fundamentals. 1. What is TypeScript?. TypeScript is a…

TypeScriptgeneral

Advanced Types (Generics & Utility Types)

TypeScript Advanced Types. Generics. // Generic function function identity<T>(arg: T): T { return arg; } const num = identity<number>(42); // Explicit const str = identity('hello'); // Inferred //…

Concepts to know for System Design

DNS Resolution: From Name to IP AddressHow a resolver walks root, TLD and authoritative servers to turn a name into an address, why TTL caching explains "propagation", and where DNS breaks.Intermediate·13 min Load Balancing: L4 vs L7, Algorithms, Health ChecksWhat L4 and L7 balancers actually forward, why least-request beats round robin, how health checks and draining make deploys safe, and why gRPC breaks it.Intermediate·13 min Caching StrategiesCache-aside, read-through, write-through and write-behind, keeping a cache correct with TTLs, invalidation and versioned keys, and surviving stampedes.Intermediate·13 min CAP Theorem in PracticeWhat CAP really constrains (only behaviour during a partition), why "pick two" is wrong, and how PACELC, quorums and consistency models become design choices.Intermediate·14 min Consistent HashingWhy hash(key) mod N remaps everything when N changes, how a hash ring moves only 1/N of keys, what virtual nodes fix, and where rendezvous, jump and Maglev fit.Intermediate·12 min Event Sourcing and CQRSStoring state as an append-only log of events, rebuilding it by replay, and serving reads from separate projections, plus the costs: versioning and stale reads.Advanced·15 min

Related stacks

API Design Agile Agile Methodology Algorithms Apache Authentication & Authorization C C++CI/CD Best Practices CQRS CUDA Caching Strategies

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