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Lessons (35)

• Vertical Slice Architecture & the Modular Monolith

  … everything needed for "Place order" lives together.  Layers …

• Two Pointers & Sliding Window

  … To see the next group, you don't rebuild the window; you slide it: one carriage leaves on …

• Choosing an Architecture

  … vertical slices (mostly CRUD)"] c1[search slice] c2[update price slice] end Ord -.- OrderPlaced, in-process event Bill …

• Go Fundamentals

  … fmt.Println("weekday") } Arrays, slices and maps ⭐ An array has a fixed size ( [3]int ). A slice is …

• Sorting Algorithms

  … right[j++]); // <= keeps it stable } return result.concat(left.slice(i), right.slice(j)); } Why n log n …

• DSA Interview Patterns Cheat Sheet

  … Contiguous subarray<br/ or substring?} B -- yes SW[Sliding window / Prefix sums] B -- no C{Tree or graph …

• Rust: Ownership, Borrowing and Lifetimes

  … Covers Cargo, move vs copy vs clone, &T vs &mut T, String vs &str, slices and reading borrow …

• Capacity Planning, SLOs and Error Budgets

  … true Turn user promises into capacity headroom, measurable SLIs and a policy for consuming the error budget. Practical …

• DBMS Foundations, Keys & Normalization

  … entities and relations; view level exposes a useful slice. A functional dependency A - B means A determines B …

• Layered (N-Tier) Architecture

  … discount codes"] -- P[presentation/] F -- B[business/] F -- D[persistence/] F -- M[migrations/] Vertical slice architecture (a later …

• Big-O Notation Made Simple

  … includes(x) , arr.indexOf(x) O(n) arr.slice() , [...arr] , arr.concat() O(n) arr.shift() , arr.unshift …

• What Is Software Architecture?

  … Hexagonal<br/ (Ports & Adapters)"] O[Onion] V[Vertical slices] end subgraph Dom["Modelling the business"] DDD[Domain-Driven …

• Observability: Logs, Metrics & Traces

  … are now traced automatically SLIs, SLOs and error budgets Term Meaning Example --- --- --- SLI (indicator) What you measure % of …

• Capacity, Availability, Latency and CAP

  … Availability is more valuable. Product search Show a slightly old index Checkout will verify later. Say what a …

• StatefulSets, DaemonSets, Jobs and CronJobs

  … Indexed ) give each pod a number so it can process its own slice of data. CronJob: a Job …

• Cluster Networking, DNS and NetworkPolicies

  … A pod that fails its readiness probe is removed from the slice. Service types recap Type Reachable from …

• What Is Clean Code?

  … C[Changes take longer] C -- D[More bugs slip in] D -- E[Even more pressure to rush] E …

• Stacks & Queues

  … Deque (double-ended) Add/remove at both ends Sliding window maximum Priority queue Highest priority out first ER …

• Arrays & Strings

  … s[0] = "b"; // silently ignored s = "b" + s.slice(1); // "bat": a brand-new string ⚠️ Building a string …

• Behavioral Patterns I: Observer, Strategy, Command, State

  … text += value; }, undo: (editor) = { editor.text = editor.text.slice(0, -value.length); }, }); const editor = new TextEditor(); editor.execute …

• Docker & Containers

  … pgdata")] Best practices - ✅ Use small, official base images ( -alpine , -slim , distroless) and pin versions ( node:22.9-alpine …

• Kafka Producers

  … fill a batch Higher = bigger batches, better throughput, slightly more latency batch.size Max bytes per batch per …

• Choosing a Programming Language

  … the compiler finds every caller Relies on tests Speed of writing a script Slightly slower Fastest Documentation Types …

• Deploying & Operating Microservices

  … work with both versions. Canary ⭐ Send a small slice of real traffic (1% → 5% → 25% → 100%) to the …

• Scaling, Load Balancing & Rate Limiting

  … bursts at window edges Sliding window Count over the last 60 s Smoother, slightly more work Token bucket …

• DynamoDB Modeling, RDS Scaling and Data Resilience

  … for read scale - Asynchronous, so reads can be slightly stale ( replica lag ). - Route reporting and read-heavy queries …

• React Hooks in Practice

  … urgent so typing stays responsive useDeferredValue Show a slightly stale value while the new one renders useActionState Handle …

• Async JavaScript: Promises, async/await and Node's Event Loop

  … i < items.length; i += limit) { const batch = items.slice(i, i + limit); results.push(...(await Promise.all(batch …

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

  … path, "utf8"); } parse(text) { return text.split("\n").slice(1).map((line) = line.split(",")); } } class JsonImporter extends DataImporter …

• C4 Architecture Diagrams: Context, Container, Component and Code

  … It might be a NestJS module, a feature slice, a package or a service class. It is not …

• Clean Architecture in Depth

  … Keep simple reads simple (see CQRS and vertical slices) When to use it ✅ Rich business rules, a long …

• Python Fundamentals

  … ordered, changeable fruits.append("cherry") fruits[0], fruits[-1], fruits[1:3] first, last, slice point = (3, 4 …

• Collaborative Document Editing & Real-Time Sync

  … of scope (say it out loud): spreadsheet and slide engines, full-text search, rendering and layout. 2. Back …

• Caching & Redis

  … Stale-while-revalidate Return a value that is slightly stale while one background request refreshes it. This keeps …

• Practical Lab: S3 File Upload and CloudFront Delivery with NestJS

  … A presigned URL is a temporary, single-purpose permission slip: your API signs it, the browser uses it …