A client opens an SFTP connection and never lets go. Maybe it’s a scheduled job that lost its network path mid-transfer, maybe it’s a misconfigured script retrying without backing off; either way, the connection sits open, holding a slot on your server indefinitely. Multiply that by a few dozen clients doing the same thing, and legitimate transfers start queuing behind connections that are never going anywhere.
That’s the kind of operational friction SFTP Gateway 3.9 is built to remove. The release is live on Docker Hub now, with AWS, Azure, and Google Cloud Marketplace listings following in the coming days. Docker gets it first, so if you want the new features immediately, that’s the fastest path — SFTP Gateway’s Docker deployment guide walks through spinning up a container in minutes. For more on this, check out this YouTube video on deploying SFTP Gateway using Docker.
Three Features Worth Knowing About
Connection Throttling lets you cap the number of simultaneous SFTP connections at the instance level, per IP address, or per user, with a default limit of 50. Instead of discovering a resource problem after the fact, you set the ceiling up front, so one client — or one bad actor running a connection-flood script — can’t hold your server hostage while everyone else waits in line.
On-the-Fly Zlib Compression is now negotiated during the SSH key exchange. If a client like FileZilla requests it, SFTP Gateway compresses data in transit, without requiring your users to zip files by hand first. For transfers over constrained or metered connections, that’s a meaningful speed improvement with zero workflow change on the client side.
Audit-Ready Key Exchange Logging means the audit log now captures the full key exchange negotiation: what the server offered, what the client requested, what they agreed on, and critically, why a match failed when it does. If your compliance team has ever had to reconstruct why a connection was rejected, this closes that gap. The answer is in the log, not in a packet capture.
Under the Hood: A Stack Upgrade With a Deadline Attached
SFTP Gateway 3.9 also moves the underlying stack to Spring Boot 4.1 on Java 21, with support for PostgreSQL 18, as confirmed in the official release notes. That’s not just routine housekeeping. If your deployment’s database backend is still running PostgreSQL 13, standard support has already ended on Amazon RDS and Aurora — AWS closed it out on February 28, 2026. What’s left is Extended Support, which AWS bills through February 2029 at an added per-vCPU-hour surcharge for staying on an unsupported major version. Moving your backend to PostgreSQL v3.9 means you’re no longer paying that premium to stand still.
The release also ships smaller container images, additional SSH hardening, including denying unauthorized port-forwarding requests and JWT issuer allowlisting for identity provider logins, and dependency updates that clear several HIGH-severity CVEs (full details in the release notes). Both SFTP Gateway 3.9 and the upcoming StorageLink 1.3.0 also ship hardened containers built to run under strict OpenShift security policies: non-root by default, no extra capabilities required, and a mostly read-only disk structure.
Your Upgrade, Your Timeline
Because SFTP Gateway runs inside your own cloud account, none of this arrives as a forced update. You decide when to move to 3.9, and you can test it against your own change control process first — the trade-off is that you also own the decision of when that PostgreSQL 13 extended-support bill starts landing on your AWS invoice.
Full upgrade guidance is in our Knowledge Base. If you want help mapping the upgrade path for your specific environment, reach out to support@thorntech.com.
About Thorn Technologies
Thorn Technologies specializes in cloud-native file transfer solutions for enterprises. Our SFTP Gateway and StorageLink products serve organizations worldwide, delivering the security and reliability of traditional managed file transfer solutions with the flexibility and cost efficiency of modern cloud infrastructure.
