Sling is a free, open-source ELT command-line tool with a core engine written in Go. It extracts data from a source database, warehouse, or file storage and loads it into a target, and it does this well: a streaming design keeps memory use low, wildcard replication moves many tables at once, and modes like full-refresh, incremental (merge or append), snapshot, and backfill cover common movement patterns. It supports 40-plus connectors across databases and object stores (S3, GCS, Azure Blob, SFTP), and its CLI Pro tier adds REST API extraction, change data capture, and schema migration.
Teams look for a Sling alternative for different reasons. Some want a Python-native library they can embed in their own code, some need a large managed connector catalog with a hosted control plane, and some want ingestion to live inside a broader pipeline that also handles transformation, quality checks, and orchestration. There is no single best answer here: the right tool depends on the job you are actually doing, the stack you already run, and whether you want to operate infrastructure yourself or pay someone else to.
Bruin belongs on this shortlist when ingestion is one step in a larger pipeline rather than a standalone task. Bruin is an open-source, CLI-first end-to-end platform: it uses ingestr for ingestion, runs SQL and Python transformations with built-in data quality checks, and offers Bruin Cloud for orchestration, catalog, lineage, and RBAC. If you only need to replicate tables between two databases, a focused tool like Sling or ingestr may be a better fit. If you want ingestion, transformation, and scheduling in one framework, Bruin is worth evaluating.