[JorgeGT]

Also, both Landsat and Sentinel (which is still free but has higher resolution, 10m/px, without needing pansharpening) data is available on AWS:

L8: https://aws.amazon.com/es/public-datasets/landsat/

S2: http://sentinel-pds.s3-website.eu-central-1.amazonaws.com/

[llccbb]

https://landsatonaws.com has a nice interface I think.

API is https://landsatonaws.com/{path}/{row}/{scene}