Depends on the job and definition of performing, but if you’re a software developer (which is all I have for context), then yeah, you might be able to pull off

Depends on the job and definition of performing, but if you’re a software developer (which is all I have for context), then yeah, you might be able to pull off the bare minimum of performance - which is completing whatever feature requests are coming from the product manager or client. But if you are working on a team as anything above an entry level developer - the job description is more than that. If you have extra time in your work week, you should be looking at ways to make your team better - what parts of the project are painful and can be improved? You should be looking out for your teammates, particularly those with less experience - and asking them if they need help. You should be coordinating with other teams that are doing similar work. Are there ideas you can offer to them to help their work, and in turn do they have ideas that can help you and your team? Essentially, most jobs are social, and that’s embedded into the job requirements. You have to talk to people when they are working. If you’re working two jobs over everyone else’s 9 - 5, you cannot do this as effectively as someone with one “full time” job.