Fluentd is the main competitor of Logstash. It is also the tool of choice of some cloud providers.
Thanks to its modular approach with the use of plugins, you can find plugins for data sources (such as Ruby applications, Docker containers, SNMP, or MQTT protocols), data outputs (such as Elastic Stack, SQL Database, Sentry, Datadog, or Slack), and several other kinds of filters and middleware.
Fluentd should be lighter on resources than Logstash, but it is still not a perfect solution for running at scale. The counterpart to Filebeat that works with Fluentd is called Fluent Bit.