exactly-once

QueenMQ is a new generation distributed message broker, able to sustain millions of messages per second.

Example gaming leaderboard application covering streaming ingestion, CDC enrichment, processing and visualisation including demo of advance real-time analytics concepts like late data arrival, exactly-once, dynamic config, archival and on-demand replay

Safe request retries for Spring Boot REST APIs — @idempotent + Idempotency-Key header, Redis and JDBC stores.

The Inbox Pattern/Process for Laravel apps. Ensure the ordering, uniqueness, and reliable handling of webhook requests.

Stateful actors on Apache Flink 2.x and Java 21 — durable per-key state, exactly-once messaging, Kafka and Kinesis I/O, Kubernetes-native deployment. Continues the Apache Stateful Functions programming model on the modern Flink line.

Exactly-once + circuit breaker for agent tool calls (loops, retries, duplicate side effects)

A stream processing engine that stays correct when processes die. SQL or typed C++ over event time and keyed state, with exactly-once delivery and twenty-plus connectors: brokers, CDC, databases, lakehouse tables, graphs. The same pipeline runs on a single machine, inside a service or scaled out across a highly available cluster. Arrow-native C++.

Lightweight Python message queuing with Redis and built-in publish-side deduplication.

Riffl - generic streaming data ingestion framework

Async Python framework for exactly-once Kafka services

Vibe-code durable AI workflows over sensitive data. The compiler refuses to build one that leaks, loops forever, or pays twice; the runtime makes every external action durable and exactly-once.

Self-hosted control plane for AI video production: an exactly-once job ledger, a documented remote-worker protocol, TTS narration, subtitle alignment and FFmpeg assembly, with pluggable providers.

Observer/Learner replicas for Apache Kafka — sync without joining the ISR; promote in seconds with zero data movement. Reference implementation with real-cluster evidence.

Wrappers for Apache Kafka java clients

Interactive browser simulator that visualizes delivery guarantees, idempotency, DLQ, Outbox and Inbox patterns across Azure Service Bus, Event Hubs, Event Grid, Kafka, RabbitMQ and more. Built for teaching Event-Driven Architecture.

Robust, Stripe-grade idempotency key middleware & decorator for FastAPI / Starlette with pluggable backends (Memory, SQLite, Redis)

3 Problems from SP04 to be solved using HashMap/ HashSet instead of TreeMap/ TreeSet.

A full agent framework on the Vercel AI SDK, durable from the core: exactly-once tool calls, deterministic replay, time-travel.

Verified Effect Commit Protocol for AI agents — seal the intended effect, witness the actual outcome.

Distributed stream processing engine in Go: gRPC ingestion, event-time windows, backpressure, Chandy-Lamport checkpoints, exactly-once, cluster mode with automatic recovery