Also following the end of slavery the British Empire used “Coolies” from India and Asia in various transportation and labour roles which were basically a transitionary role between slavery and free paid workers. So job-wise was somewhat similar to slavery, in practice, but largely voluntary at the source and paid in some form to their families or community rather than ‘stolen’ by slave traders. While also less constrained from leaving back to their home countries, which was still difficult and they were not compensated nearly enough.

https://en.m.wikipedia.org/wiki/Coolie