adk-backend

In-depth API contract design knowledge - REST (OpenAPI 3.x/3.1), GraphQL, RPC (gRPC/Protobuf), and asynchronous message contracts for Kafka/RabbitMQ/Pub-Sub under the AsyncAPI 3.x standard (the same role as OpenAPI, but for messages instead of REST). Covers design principles, security (OWASP API Security Top 10), naming/versioning, and standardized error format (RFC 7807). Use before implementation, to finalize the communication contract before writing code.

In-depth database design and server-side optimization knowledge - RDBMS (Oracle, PostgreSQL, MySQL) and NoSQL (document: MongoDB; key-value: DynamoDB/ScyllaDB Alternator; column-based: Cassandra/ScyllaDB CQL). Transaction isolation, concurrency control/locking, indexing/EXPLAIN, query optimization, schema/data-model design, advanced PostgreSQL/MySQL tuning (JSONB, extensions, VACUUM, replication), partition/shard key design, migration. Use when a feature needs schema design/changes or query optimization against a server-based database.

In-depth Elasticsearch knowledge - index/mapping design, analyzers, Query DSL, aggregations, reindex strategy, shard/replica sizing. Use when the feature needs full-text search or analysis/aggregation over large datasets.

In-depth Java + Spring ecosystem knowledge (Spring Boot 3.x, Java 21) - Spring MVC/WebFlux, Spring Data JPA, Spring Security 6 (JWT/OAuth2), Spring Cloud (Config/Eureka/Gateway)/Resilience4j, package structure (package-by-layer vs. package-by-feature, Spring Modulith, cross-module transactions), Java code style/formatting (Google Java Style, Spotless/Checkstyle), plus unit + integration testing (JUnit5, Mockito, Testcontainers). Does NOT cover Kafka/RabbitMQ (see `messaging-skill`), API contract design (see `api-contract-skill`), or DB schema design (see `database-skill`). Use when implementing Java/Spring business logic.

In-depth broker knowledge for asynchronous messaging - Apache Kafka (topic/partition design, consumer groups, delivery semantics, idempotency, schema evolution, dead-letter topics, consumer lag) and RabbitMQ (exchange types, routing, queue durability, dead-letter exchange, prefetch, quorum and priority queues), plus how to choose between them. Use when a feature publishes or consumes messages through a broker. If the request only says "async processing" with no technology named, check the project's actual dependency first rather than defaulting to either.

Sets up continuous production observability - structured logging pipelines, Prometheus/Grafana metrics and dashboards, distributed tracing, and alerting rules - plus application profiling and capacity forecasting from real production trends. Use when adding observability to a service, debugging production issues via logs/metrics/traces, profiling CPU/memory bottlenecks, or forecasting capacity needs. For a one-off load test gating a merge or release as part of the QA test lifecycle (pass/fail, defect report), use `test-master` instead - this skill's load-testing content targets capacity/production-readiness validation, not CI gating.

In-depth Redis knowledge - caching, distributed locks, lightweight queues, ranking/leaderboards. Use when the feature needs a cache, a distributed lock, a queue that can tolerate minimal loss, or a leaderboard. If strong durability/delivery guarantees are needed (retry, dead-letter, replay), see `messaging-skill` instead of Redis.

Manage this plugin's bundled toolbox MCP server (mcp/toolbox/) - full CRUD for database connections (PostgreSQL, MySQL, TiDB, Redis, MongoDB, or any other type Toolbox supports) and their tools. Create a connection/tool (checking for an existing target match first, and a read-only permission check for connections), read/list existing ones (secrets redacted), update values on an existing connection/tool, or delete either. Always applies a write through validate.sh's snapshot/check/restore flow. Use for any add/list/show/edit/update/remove request about a toolbox connection or tool. Do NOT use for a different third-party MCP server, or for authoring toolbox/a new MCP server (`mcp-developer`).