Syncle: keep any two databases in sync, live and across engines

You have a row in Postgres. You want that same row in MongoDB — not tonight in a batch job, but the instant it changes. And next month you'll want it in Redis too, and maybe POSTed to some webhook. Today that's a Kafka cluster, a Debezium connector, a sink connector, a schema registry, and a weekend. For a job that is, at its heart, one sentence: a source → one or more destinations → kept in sync. Syncle is an open-source tool that does exactly that sentence, and nothing you didn't ask for. Connect your databases, draw a bridge from a source to one or more destinations, and the moment a row changes in the source it's written to every destination you linked. Any engine to any engine — PostgreSQL · MySQL/MariaDB · SQLite · MongoDB · Redis — plus HTTP endpoints when you need them. This post is a tour of what it does and, for the curious, how it's built. The core idea: a bridge A bridge reads rows from a source and writes each one to its destinations . A destination is either: another database — the headline feature. Postgres → MongoDB, MySQL → SQLite, MongoDB → Redis. One bridge can fan out to several databases at once, and bridges can chain (A → B → C). an HTTP endpoint — POST/PUT/PATCH each row to a URL with a payload you design, for feeding a service instead of a database. The interesting part isn't that it copies data — plenty of things copy data. It's the guarantees around how . No duplicates, ever Every database write is an idempotent upsert , keyed by columns you choose. So replays, retries, and at-least-once redeliveries never double-write. Under the hood each engine does it with its own native atomic operation: Engine Upsert PostgreSQL / SQLite INSERT ... ON CONFLICT MySQL INSERT ... ON DUPLICATE KEY UPDATE MongoDB updateOne(filter, ..., { upsert: true }) Inserts, updates, and deletes all propagate — a delete routes to a keyed delete on each target. Missing table? It builds it If the destination table or collection doesn't exist, Syncle creates it from the sou