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Lessons (33)

• Collaborative Document Editing & Real-Time Sync

  … docId, rev)] CS -- ephemeral -- PS[Pub/Sub<br/ presence + relays] LOG -- SNAP[Snapshotter] SNAP -- BLOB[(Blob store<br …

• Event-Driven Patterns, Step Functions and Reliable Lambdas

  … to avoid cold starts SnapStart (Java and some runtimes) Restores from a snapshot for faster start Reduce cold …

• AWS Messaging: Queues, Topics and Events

  Use SQS to hold work, SNS to fan out notifications, and EventBridge to route events without tightly coupling …

• Behavioral Patterns II: Chain, Template, Iterator, Mediator, Memento, Visitor

  Six more behavioral patterns, from Express-style middleware chains to undo snapshots, each with a picture and a …

• CQRS & Event Sourcing

  … LR ES[(Event store<br/ append-only)] -- Snap["📸 Snapshot every 100 events"] ES -- P1[Projection: balances] ES …

• YAGNI: You Aren't Gonna Need It

  … packing for a weekend trip. "What if it snows? What if there's a wedding? What if I …

• Which Pattern Do I Need?

  … Memento stores snapshots to restore. Composite vs Decorator Both wrap objects. Composite groups many children ; Decorator wraps exactly …

• Cost Optimization and the Well-Architected Framework

  … unused EC2, unattached EBS volumes, old snapshots, idle load balancers, dev environments running overnight. 2. NAT gateway data …

• The Hot SKU Alert Problem

  … and job state Snapshot watchers to object storage Stable, replayable audience Extra storage and snapshot freshness concerns Use …

• Kafka vs RabbitMQ & the Kafka Ecosystem

  … Elasticsearch, S3, Snowflake, BigQuery, MongoDB, Postgres. json { "name": "orders-cdc", "config": { "connector.class": "io.debezium.connector.postgresql.PostgresConnector …

• Internals, Upgrades, Resilience and Interview Questions

  … Restore members or recover from a snapshot, which is why regular tested backups matter. Remember this - The API …

• Multi-Account Strategy, Governance and Security Operations

  … severity = 7] E -- N[SNS / chat alert] E -- L[Lambda: isolate instance, disable key] Preventive controls checklist - Block …

• Frontend Security

  … shown as text, not executed Where XSS still sneaks in jsx // ❌ 1. dangerouslySetInnerHTML with user content <div dangerouslySetInnerHTML …

• Code Profiling

  … Compare heap snapshots after a full GC at a healthy baseline and after repeatable growth. ts // Risky: grows …

• Environments, Workspaces, and Multiple Accounts

  … Add the module's required inputs here. } This snippet illustrates wiring, not a complete module invocation. A child …

• EC2, Storage and Auto Scaling

  … Inspect snapshots, retained volumes, and IP resources when cleaning up. See [EC2 termination behavior](https://docs.aws.amazon …

• AWS Databases: Choose the Right One

  … you need a final snapshot, then delete the instance and review remaining snapshots/storage. Never skip backup decisions …

• Drift, Troubleshooting, and Disaster Recovery

  … Preserve the current state snapshot and logs in restricted storage. 3. Compare cloud inventory, resource addresses, and available …

• Meaningful Names

  … Collection plural users , orderItems userList2 , arr Constant UPPER SNAKE MAX RETRIES , TAX RATE n , x mermaid flowchart LR …

• Linked Lists

  … next only"] s1[A] -- s2[B] -- s3[C] -- sn[null] end subgraph Doubly["Doubly linked: next and prev …

• React Fundamentals

  … small, reusable bricks ( components ) snap together into bigger ones, and the bigger ones form the whole page. And …

• Service Communication: Sync vs Async

  … Tools Temporal, AWS Step Functions, Camunda Kafka, RabbitMQ, SNS/SQS Choosing a style mermaid flowchart TD Q1{Does …

• Message Queues & RabbitMQ

  … throughput, replay (see the Kafka lessons) AWS SQS / SNS Managed queue / pub-sub Serverless, no ops Redis Streams …

• Kafka Producers

  … partition Bigger = fewer requests compression.type none , gzip , snappy , lz4 , zstd Smaller network and disk usage for some …

• Event-Driven Architecture

  … channel / broker Delivers events to consumers Kafka, RabbitMQ, SNS/SQS, EventBridge, NATS Event consumer Reacts to events it …

• Resilience, Disaster Recovery and Multi-Region Design

  … read replica or automated backup replication EBS / EC2 Snapshots copied cross-region; AWS Elastic Disaster Recovery for servers …

• DynamoDB Modeling, RDS Scaling and Data Resilience

  … to 35 days) into a new instance Manual snapshots Kept until deleted; can be copied across regions and …

• Frontend Testing Strategy

  … btn-primary Find by role "button" named "Save" Snapshot of the whole DOM Specific assertions on what matters …

• AWS Data Pipelines in Plain Language

  … Decide whether reports are immutable snapshots, revised partitions, or views over corrected data. Store an event time and …

• Cross-Service Data: How to Join Without a Database JOIN

  … A replay job rebuilds the projection from retained events or a snapshot. This gives fast reads without a …

• Backend Design Scenarios

  … Cache the first page, expire or trim old entries, and use a stable snapshot/cursor so pagination does …

• Caching & Redis

  … 100) throw new TooManyRequestsError(); Persistence and availability - RDB snapshots: save the whole dataset every N minutes (fast restarts …

• Practical Project: Deploy a Real CRM App on EKS

  … PodDisruptionBudget. - [ ] Enable RDS Multi-AZ and test a snapshot restore. 20. Clean up (avoid surprise bills) Delete in …