NestJS

Architecting secure stateless authentication: token structure, HTTP-only cookie storage against XSS/CSRF, automated rotation family tracking, and Redis blacklisting.

Architecting bulletproof password recovery: secure token hashing, timing attack mitigation with timingSafeEqual, OTP brute-force limits, and single-use invalidation.

Demystifying Cross-Origin Resource Sharing: Same-Origin Policy, simple vs preflighted requests, credentials mode, and secure server headers.

Preventing orphaned users and lost verification emails during network outages using the Transactional Outbox Pattern and asynchronous publishing.

Comparing Database-per-Tenant, Schema-per-Tenant, and Shared Database with Tenant Discriminator: connection pooling, tenant isolation, and migrations.

Designing fault-tolerant distributed systems: Circuit Breaker states, exponential backoff with full jitter, graceful fallbacks, timeouts, and bulkheads.

A comprehensive developer guide exploring containerization internals, Docker vs VMs, multi-container Compose, and enterprise Kubernetes cluster orchestration.

Detailed architectural comparison of REST and GraphQL: over/under-fetching, DataLoader batching, HTTP edge caching vs query parsing overhead.

Preventing double-charges, ensuring transactional integrity across gateways, distributed idempotency locks, webhook retries, and automated reconciliation.

Eliminating server bottlenecks via direct client-to-storage uploads, pre-signed URL generation, magic-byte sniffing, virus scanning, and asynchronous processing.

Deep-dive into Cache-Aside, Write-Through, Write-Behind, Cache Stampede / Thundering Herd mitigation, and distributed Redis cluster strategies.

Architecting asynchronous job queues, streaming database queries, memory-bounded processing, failure retries, and job status polling/notifications.

System design for large video ingestion: chunked S3 uploads, async worker transcoding clusters with FFmpeg, HLS manifest generation, and CDN edge delivery.