Spring AI Alibaba Support Assistant: Tools, Memory, and RAG
Build a support assistant with Spring AI Alibaba and Qwen while keeping identity, authorization, memory, tools, and policy retrieval under application control.
SUM(DISTINCT) vs JOIN Duplicates: Keep Payment Identity
Learn why SUM(DISTINCT amount) can discard valid payments, how SQL deduplicates rows, and when to use payment identity, EXISTS, or explicit allocation.
SQL SUM Double Counting in One-to-Many JOINs
A reproducible SQL example shows why one-to-many JOINs inflate totals and how to fix double counting without hiding valid payments.
Sentinel Resilience: Limits, Circuit Breakers, and Fallbacks
A practical Java guide to containing slow dependencies with rate limits, concurrency caps, timeouts, Sentinel circuit breakers, and business-safe fallbacks.
OpenFeign in Java: Timeouts, Retries, and Idempotent Order APIs
Design OpenFeign order APIs with timeouts, bounded retries, idempotency keys, fallbacks, and connection budgets. Includes reproducible failure tests.
Distributed Workflow Ordering: Why Event Timestamps Fail
See how clock skew breaks event ordering, then compare fixed clocks, monotonic timing, Lamport clocks, and order versions in Java.
Reliable Java Messaging: Outbox, Idempotency, Recovery
Build a reliable Java payment-to-reward workflow with a transactional outbox, idempotent consumers, stable reward keys, refund handling, and reconciliation tests.
Distributed Locks in Java: Redis, Redlock, ZooKeeper, and Fencing
A practical guide to Java distributed locks: protect inventory with database invariants, use Redis leases safely, fence stale workers, and test Redlock and ZooKeeper failure cases.
Distributed Transactions in Java: Outbox, TCC, and Saga Compared
A Java order workflow compares local transactions, the transactional outbox, TCC, and Saga using concrete failure paths for inventory, payment, rewards, and refunds.