Database

Authentication, authorization, and security configuration with Spring Security including JWT, OAuth2, and method-level security

Testing patterns for Spring Boot applications including unit tests, integration tests, sliced tests, and test containers

Reactive programming with Spring WebFlux including Mono, Flux, non-blocking I/O, and reactive data access

Common Table Expressions and recursive queries for hierarchical data, graph traversal, and complex query composition

Index types, design strategies, and maintenance for optimal query performance in relational databases

JSON storage, querying, indexing, and manipulation in PostgreSQL and MySQL for semi-structured data

Database schema migration strategies for safe, reversible, and zero-downtime changes to production databases

Use this skill when working with PostgreSQL specifically. Activate when users mention postgres, postgress, postgresql, psql, EXPLAIN ANALYZE, VACUUM, autovacuum, bloat, WAL, connection pooling with pgbouncer, JSONB, partitioning, logical replication, RLS, or when they need Postgres-specific tuning, migration safety, or incident diagnosis.

Techniques for analyzing and optimizing SQL query performance using execution plans, statistics, and query rewrites

Stored procedures, functions, and triggers for encapsulating business logic and automating actions within the database

Transaction management, ACID properties, isolation levels, and concurrency control in relational databases

SQL window functions for analytics, ranking, and running calculations over partitioned result sets

Disk partitioning, filesystems, LVM, RAID, mount management, and storage monitoring on Linux

Linux file permissions, ownership, special bits, ACLs, and file attribute management

Log management with journalctl, rsyslog, logrotate, and centralized logging strategies on Linux

Linux networking tools including ss, ip, iptables, nftables, and diagnostic utilities

Process lifecycle, monitoring, signals, cgroups, and performance analysis on Linux systems

Bash scripting patterns, control flow, text processing, and automation for Linux administration

Systemd service units, timers, targets, and dependency management for Linux init systems

User and group management, sudo configuration, PAM, and SSH access control on Linux

Core regular expression syntax including character classes, quantifiers, anchors, and alternation

Practical regex patterns for validating emails, URLs, IP addresses, and other common string formats

Regex patterns for parsing structured and semi-structured log files from common servers, applications, and systems

Lookahead and lookbehind assertions for matching patterns based on surrounding context without consuming characters

Named capture groups for readable, maintainable regex patterns with structured data extraction

Regex performance optimization, catastrophic backtracking prevention, and engine internals for writing efficient patterns

Regex-powered find and replace patterns for text transformation, refactoring, and data reformatting

Regex patterns for extracting structured data from unstructured or semi-structured text sources

Apollo Client with React for querying, mutating, and caching GraphQL data

Apollo Server setup, configuration, plugins, and production deployment patterns

Authentication and authorization patterns for securing GraphQL APIs

Type-safe GraphQL development with graphql-codegen for TypeScript

Cursor-based pagination following the Relay connection specification

Resolver patterns, data loading strategies, and the N+1 problem in GraphQL

Schema design principles for building maintainable, intuitive GraphQL APIs

Real-time GraphQL subscriptions with WebSockets and server-sent events

Drizzle ORM for lightweight, type-safe SQL in TypeScript with zero dependencies, SQL-like syntax, and schema-as-code

Knex.js SQL query builder for Node.js with schema building, migrations, seed files, and support for PostgreSQL, MySQL, and SQLite

Kysely type-safe SQL query builder for TypeScript with zero overhead, full autocompletion, and no code generation

MikroORM for TypeScript with Unit of Work, Identity Map, decorator-based entities, and support for SQL and MongoDB

Mongoose ODM for MongoDB with schema validation, middleware hooks, population, virtuals, and TypeScript support in Node.js

Prisma ORM for type-safe database access with auto-generated client, migrations, and schema-first modeling in TypeScript/Node.js

Sequelize ORM for promise-based SQL database access with model definitions, associations, migrations, and transaction support in Node.js

TypeORM for decorator-based entity modeling, migrations, and Active Record or Data Mapper patterns in TypeScript/Node.js

API key generation, hashing, rotation, scoping, and rate limiting patterns

JWT creation, validation, refresh token rotation, and secure token storage patterns

Multi-tenant authentication isolation, tenant-scoped tokens, and data boundary enforcement

OAuth 2.0 authorization code, PKCE, client credentials, and token exchange patterns

Passkeys and WebAuthn implementation for passwordless authentication

Role-based access control design, permission hierarchies, and enforcement patterns

Server-side session handling, cookie security, session stores, and fixation prevention

SSO and SAML integration for enterprise identity federation and service provider setup

Chat room architecture covering message routing, history, moderation, and scalable room-based real-time systems

Real-time collaborative editing with CRDTs and Operational Transform for conflict-free concurrent document editing

User presence system design for tracking online/offline status, typing indicators, and activity in real-time apps

Reconnection and offline resilience patterns for WebSocket apps including retry strategies and state synchronization

Scaling WebSocket applications with Redis pub/sub, sticky sessions, horizontal scaling, and load balancing strategies

Server-Sent Events (SSE) patterns for efficient unidirectional real-time streaming from server to client

Socket.IO patterns for event-driven real-time communication with automatic reconnection and room management

WebSocket API fundamentals including connection lifecycle, message framing, and browser/server implementations