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Lessons (31)

• Caching, Consistent Hashing and Sharding

  Move reads close to users, distribute data safely, and understand cache and database consistency costs. Three different tools …

• Time, Consistency and Distributed Transactions

  Reason about clocks, ordering, split brain, locks, CRDTs and transactions without promising impossible global certainty. ![Distributed correctness: clocks …

• ACID, Transactions & Locks

  … Keep transactions short, access tables in a consistent order, avoid network calls inside them, and monitor lock-wait …

• Transactions, Indexes & Concurrency

  … Atomicity is all-or-nothing; consistency preserves constraints; isolation defines concurrent visibility; durability survives failure. Never wait for …

• Event-Driven Architecture

  … Easy to follow in code ❌ Spread across services Consistency Immediate Eventual Anatomy Part Role Examples --- --- --- Event producer Detects …

• SQL vs NoSQL Databases

  … Very organised, very consistent. - NoSQL is like a filing cabinet of folders : each folder (document) holds everything about …

• Finding Service Boundaries with DDD

  … consistency boundaries An aggregate is a group of objects that must stay consistent together , changed in one transaction …

• CQRS & Event Sourcing

  … eventual consistency The read model updates a moment after the write. A user might save a change and …

• Domain-Driven Design: Tactical Patterns

  … the consistency boundary ⭐ An aggregate is a group of entities and value objects that must stay consistent together …

• Design a Ride-Sharing Service

  … Locations are eventually consistent; ride assignment needs stronger ownership. Watch stale-location age, match latency, conflicts and regional …

• Design an E-Commerce Checkout

  … search and recommendations can be cached and eventually consistent. Checkout cannot: reserve inventory atomically, create/get a payment …

• Architecture Patterns at Scale

  … Event-driven Decoupled side effects Ordering, replay, eventual consistency Peer-to-peer Direct decentralized sharing Discovery, trust, NAT …

• System Design Interview Framework

  … Clarify users, core flows, scope, latency, availability and consistency. 2. Estimate peak RPS, storage, bandwidth and growth. 3 …

• Design a Social Media Feed

  Build a fast home feed with fan-out choices, durable post storage, eventual consistency and safeguards for celebrity …

• Capacity, Availability, Latency and CAP

  … a design chooses latency targets, availability targets and a partition-time consistency policy](/img/system-design-l6/capacity …

• Choosing an Architecture

  … reactions to the same facts, integration, buffering Eventual consistency, debugging Microkernel Small core + plug-ins Extensible products, per …

• Data in Microservices: Sagas & the Outbox Pattern

  Each service owns its database, so how do you keep data consistent across services without a shared transaction …

• The L6 System-Design Thinking Loop

  … a few seconds of stale playback position to keep playback available” is stronger than “eventual consistency is fine.”

• Meaningful Names

  … Just be consistent, and write it down for the team. Rule 5: Make names searchable and pronounceable js …

• Replication, Partitioning & Sharding

  Scale reads with replicas, split data safely with partitions and shards, and plan for consistency, hot keys and …

• Service Communication: Sync vs Async

  … can be added without touching the publisher. ❌ Eventual consistency (data is not updated everywhere instantly), harder debugging, and …

• What Is Software Architecture?

  … consistency, operating cost Performance (caching) Freshness of data, complexity Flexibility (many abstraction layers) Readability, speed of development Consistency …

• REST API Design

  … User not found } Checklist - [ ] Plural nouns, no verbs in paths - [ ] Correct methods and status codes - [ ] One consistent error …

• Scaling, Load Balancing & Rate Limiting

  … active requests Requests vary in duration IP hash / consistent hashing Same client → same server Need stickiness or cache …

• Domain-Driven Design: Strategic Design

  … Bounded contexts ⭐ A bounded context is an explicit boundary inside which one model and one language apply consistently …

• YAGNI: You Aren't Gonna Need It

  … build it (simply). - DRY keeps what you built consistent (one source of truth). When looking ahead IS fine …

• Brokers, Replication & Durability

  … better than silently risking data loss)"] 💡 Kafka chooses consistency over availability here: with too few in-sync copies …

• Monolith vs Microservices

  … calls Transactions ✅ One ACID database transaction ❌ Sagas, eventual consistency Testing end to end ✅ Easy ❌ Hard Ops cost ✅ Low …

• TypeScript Essentials

  … public APIs, type for unions and everything else. Consistency matters more than the choice. Union types and narrowing …

• Topics, Partitions & Offsets

  … bootstrap-server localhost:9092 Naming tips: use a consistent scheme such as <domain .<entity .<event : shop.orders.placed …

• Database Indexing & Transactions

  … do this for you). - Lock rows in a consistent order to avoid deadlocks. - Transactions don't span services …