Heka and Logstash are open-source data processing tools with distinct differences, primarily in their architecture and configuration. Developed by Mozilla and written in Go, Heka is praised for its performance and features a plugin system with built-in modules for data input, decoding, filtering, encoding, and output, using TOML configuration files. Conversely, Logstash, written in Ruby, is known for its simpler architecture and JSON-like configuration, which is easier for beginners to understand and configure. While Logstash offers a broader selection of plugins and a more robust community, making it more accessible for large data processing tasks, Heka provides advanced features like Sandboxes for anomaly detection but requires more expertise in Go or Lua for plugin development. Users considering switching from Logstash to Heka may find transitioning challenging due to differences in plugin systems and configuration languages, although Heka's solid documentation supports faster learning. Despite these challenges, Heka's performance merits attention, even as Logstash remains a popular choice within the ELK stack due to its ease of use and community support.