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Lessons (27)

• Design a File Storage Service

  Upload bytes directly to object storage while the API owns durable metadata, authorization, sharing and synchronization. ![File storage …

• Storage Engines & Database Operations

  … a bounded pool protects the primary while WAL, backups and replicas provide recoverability](/img/database/storage-operations.svg …

• ConfigMaps, Secrets & Storage

  … accessModes: [ReadWriteOnce] storageClassName: fast resources: requests: storage: 20Gi --- In the pod spec: volumes: - name: uploads persistentVolumeClaim: { claimName: uploads …

• Database Internals, Replication and Scaling

  Connect storage-engine choices, durability, replicas, query plans, pooling and data layout to real production behaviour. ![Database path …

• Design a Chat Application

  … presence and offline notifications. ![Chat separates durable conversation storage from WebSocket fan-out, presence and offline push paths …

• Design a URL Shortener

  … Redirects read edge/cache then durable storage; click analytics is asynchronous. Protect users with rate limits, phishing scans …

• Design a Polite Web Crawler

  … a URL frontier schedules polite fetches while deduplication and storage process discovered links](/img/system-design-l6/web …

• Why Kubernetes?

  … Configuration and sensitive values Config & Storage PersistentVolume Storage that outlives pods Config & Storage HPA Autoscaling pods based on …

• Design a Logging and Monitoring Platform

  … Measure ingestion lag, dropped samples, query latency, cardinality and storage cost.

• System Design Interview Framework

  … 2. Estimate peak RPS, storage, bandwidth and growth. 3. Draw the smallest core path. 4. Model data and …

• Big Data: ETL, Warehouses and Streaming

  … A data lake holds raw/flexible data; a warehouse optimizes governed analytical queries; a lakehouse combines lake storage …

• 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

  … peak RPS, bytes per request, read/write ratio, storage growth and concurrent users. Throughput is work per second …

• Views, Triggers & Stored Procedures

  … cost each read Materialized view Reads stored result Storage and refresh delay Q24: Trigger guidance A trigger can …

• Premiere-Night Video Streaming

  … Heartbeat progress to Redis for fast resume and persist asynchronously to durable storage. Include a timestamp/sequence so …

• DBMS Foundations, Keys & Normalization

  … Abstraction, dependencies and design Physical level describes storage; logical level describes entities and relations; view level exposes a …

• L — Liskov Substitution Principle

  … to anything with a shared contract: js // Any "storage" passed in must behave like the others const memoryStorage …

• Pods

  … front door (network ports), and can share a storage cupboard (volumes). They move in and out together . Most …

• Scaling, Load Balancing & Rate Limiting

  … Keep sessions in Redis or in tokens, files in object storage (S3), and state in the database. Scaling …

• Frontend Security

  XSS, CSRF, clickjacking, token storage, CORS and supply-chain risks, explained with pictures. What can go wrong in …

• Caching & Redis

  … Treat it as a cache or as fast secondary storage, not as your only copy of critical data …

• Deployments, ReplicaSets & Rollouts

  … Elasticsearch Stable names ( db-0 , db-1 ), stable storage per pod, ordered start/stop DaemonSet One pod on …

• Docker & Containers

  … postgresql/data -e POSTGRES PASSWORD=secret postgres:17 Storage Use for --- --- Named volume Database files, anything persistent Bind …

• Authentication, Authorization & API Security

  … JWT, OAuth 2.0 and OpenID Connect, password storage, and the OWASP risks every backend developer must know …

• CQRS & Event Sourcing

  … Shape Normalised, enforces rules Denormalised, joined, pre-computed Storage Postgres (transactions) Elasticsearch (search), Redis (fast lookups), a reporting …

• Hexagonal Architecture (Ports & Adapters)

  … external services you might swap (payment providers, email, storage), long-lived systems. ❌ Thin CRUD apps with almost no …

• Clean Architecture in Depth

  … convert data between formats APIs, UI or storage formats change Use cases (and their ports) 🟣 Frameworks & drivers …