Systems Manager Automation now supports higher concurrency limits for execution
AWS Systems Manager Automation now supports higher concurrency limits when running automation executions, helping IT operators automate operational tasks at a larger scale. You can now run up to 100 concurrent automations per account – including child automations (automations that are started by another automation execution). If you attempt to run more automations, the additional automations are added to a queue of up to 1,000 executions. In addition, you can also run 25 rate control automations (automations with concurrency value and error threshold), with an additional queue of 1,000.
Source:: Amazon AWS