Mathias Paulenko

Implement centralized input validation in GraphQL using custom validation functions, Zod schemas, and input type transforms

Identify N+1 query problems in GraphQL resolvers using logging, DataLoader, and query analysis tools before they hit production

Implement GraphQL subscriptions over WebSockets with Apollo Server and PubSub for real-time updates pushed to connected clients

Set security HTTP headers in Express apps with Helmet — CSP, HSTS, X-Frame-Options, X-Content-Type-Options, and CORS for OWASP-compliant...

Fetch multiple HTTP endpoints concurrently using asyncio.gather and aiohttp with error handling, rate limiting, timeouts, and connection...

Encrypt sensitive data using AES-GCM with the cryptography library. Covers key derivation, nonce generation, authenticated encryption, and...

Implement secure JWT access and refresh token rotation in Python with blacklist, reuse detection, and automatic access token renewal for...

Implement distributed rate limiting in FastAPI using Redis sliding window and token bucket algorithms with per-user, per-IP, and...

Store, retrieve, and rotate application secrets securely using HashiCorp Vault with Python hvac client, dynamic secrets, and automatic...

Protect Python applications from SQL injection using SQLAlchemy parameterized queries, ORM models, input validation, and query inspection...

Isolate tenant data in shared infrastructure using row-level security, schema-per-tenant, or database-per-tenant strategies. A pattern for...

Chain processing steps with independent filters connected by pipes. A pattern for data transformation pipelines where each step is reusable...

Delegate authentication to external identity providers. A pattern for integrating OAuth2, OIDC, SAML, and SSO across multiple services and...

Validate claims and delegate access using signed vouchers without exposing sensitive data. A security pattern for token-based authorization...

Write effective prompts for AI models. Covers prompt patterns, few-shot learning, chain-of-thought, RAG, system prompts, temperature...

Version REST and GraphQL APIs with URI, header, query param, and content negotiation strategies. Covers deprecation, sunset, and migration...

Build unified GraphQL APIs across multiple services with Apollo Federation. Covers subgraphs, supergraph composition, entity resolution,...

Build real-time event streaming pipelines with Kafka. Covers producers, consumers, Kafka Streams, Kafka Connect, schema registry, and...

Compare sync vs async communication patterns for microservices. Covers REST, gRPC, message queues, event-driven, service mesh, and when to...

Master asynchronous Python programming with asyncio. Covers coroutines, tasks, event loops, async/await, gather, semaphores, queues, HTTP...

Deploy and scale Elasticsearch clusters. Covers node roles, sharding, replicas, index templates, mapping, snapshots, and production tuning...

Optimize PostgreSQL for high throughput. Covers configuration tuning, indexing strategies, query optimization, connection pooling,...

Build CI/CD pipelines from scratch with GitHub Actions. Covers workflows, runners, matrix builds, caching, secrets, environments,...

Deploy Kubernetes applications with GitOps using ArgoCD. Covers installation, ApplicationSets, sync strategies, Helm/Kustomize, RBAC, and...