Custom SMT for Confluent Cloud Limitations and Support
This page describes the limitations and support for Custom SMTs. Be sure to review all the information in this page before proceeding with the Quick start.
Limitations
Custom SMTs can only be used with fully-managed Connectors.
Custom SMTs scope to a specific environment and CSP, including AWS and Microsoft Azure.
Custom SMT on Azure requires Confluent CLI version 4.49.0 or later.
Only available for clusters within Private Networking setups (Peering, Transit Gateway, Private Network Interface, Privatelink) on AWS and Microsoft Azure.
Default limit for Custom SMTs per fully-managed connector is 10.
Default limit for uploaded Custom SMT artifact files is 10 per Confluent environment.
Default limit for Custom artifact file size is 100 MB.
Message size limit of ~2MB (4MB on the wire size).
Custom SMT JARs must be compiled using Java 21, Java 17 or earlier. JARs compiled with Java 25 are not supported.
Custom SMT performance does not automatically scale with the number of connector tasks. You must manually tune connector capacity for different workloads.
Reach out to Confluent Support to request limit increase for any of the current limitations.
Important
Confluent may scan files uploaded through Custom SMT to detect security risks.
Shared Responsibility
Confluent supports the underlying Custom SMT infrastructure in Confluent Cloud only. It is your responsibility to troubleshoot Custom SMT issues for connectors you build or that were provided to you from others. The following provides additional details about shared support responsibilities.
Shared responsibilities matrix
Customer Managed: The customer is responsible for self-managing these services. Confluent does not provide any support for customer-managed services and features with Custom SMTs.
Confluent Managed: Confluent is responsible for managing these services and providing support.
Supported regions
You can use Custom SMTs with fully-managed connectors in the following AWS and Azure regions supported by Confluent Cloud.
AWS regions
AWS Region | Location | Custom SMT |
|---|---|---|
us-east-1 |
| ✓ |
us-east-2 | Ohio, USA | ✓ |
us-west-2 | Oregon, USA | ✓ |
ca-central-1 | Canada Central | ✓ |
ca-west-1 | Calgary, Canada | |
sa-east-1 | São Paulo, Brazil |
AWS Region | Location | Custom SMT |
|---|---|---|
ap-east-1 | Hong Kong | |
ap-northeast-1 | Tokyo, Japan | |
ap-northeast-2 | Seoul, South Korea | |
ap-northeast-3 | Osaka, Japan | |
ap-south-1 | Mumbai, India | ✓ |
ap-south-2 | Hyderabad, India | |
ap-southeast-1 | Singapore | ✓ |
ap-southeast-2 | Sydney, Australia | ✓ |
ap-southeast-3 | Jakarta, Indonesia | |
ap-southeast-4 | Melbourne, Australia | |
ap-southeast-5 | Malaysia | |
ap-southeast-7 | Thailand |
AWS Region | Location | Custom SMT |
|---|---|---|
eu-central-1 | Frankfurt, Germany | ✓ |
eu-central-2 | Zurich, Switzerland | |
eu-north-1 | Stockholm, Sweden | |
eu-south-1 | Milan, Italy | |
eu-south-2 | Spain | |
eu-west-1 | Ireland | ✓ |
eu-west-2 | London, UK | ✓ |
eu-west-3 | Paris, France |
AWS Region | Location | Custom SMT |
|---|---|---|
me-south-1 | Bahrain | |
me-central-1 | UAE | |
af-south-1 | Cape Town, South Africa | |
il-central-1 | Tel Aviv, Israel |
Azure regions
Azure Region | Location | Custom SMT |
|---|---|---|
canadacentral | Toronto, Canada | |
mexicocentral | Mexico Central | |
brazilsouth | Sao Paulo state, Brazil | ✓ |
centralus | Iowa, USA | ✓ |
eastus | Virginia, USA | ✓ |
eastus2 | Virginia, USA | ✓ |
southcentralus | Texas, USA | |
westus2 | Washington, USA | ✓ |
westus3 | Phoenix, USA |
Azure Region | Location | Custom SMT |
|---|---|---|
australiaeast | New South Wales, Australia | |
centralindia | Pune, India | ✓ |
eastasia | Hong Kong | |
japaneast | Tokyo, Japan | |
koreacentral | Seoul, South Korea | |
southeastasia | Singapore | ✓ |
newzealandnorth | New Zealand North |
Azure Region | Location | Custom SMT |
|---|---|---|
francecentral | Paris, France | |
germanywestcentral | Frankfurt, Germany | |
northeurope | Ireland | ✓ |
norwayeast | Oslo, Norway | |
swedencentral | Gävle, Sweden | |
switzerlandnorth | Zurich, Switzerland | |
uksouth | London, UK | ✓ |
westeurope | Netherlands | ✓ |
italynorth | Milan, Italy | |
spaincentral | Spain |
Observability / Logs
You can view the Confluent Cloud Custom SMT events alongside fully-managed connector events in the Confluent Cloud Console. For more details on how to view these events, see View Connector Events for Confluent Cloud.