1. He was standing right behind her.

2. He was standing just behind her.

3. I got here right after nine.
4. I got here just after nine.

5. The bus came right on time.
6. The bus came just one time.
7. The bus came exactly on time.
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Are they all grammatical?
Are 'right' and 'just' interchangeable?

1 answer

just, used in position, connotes very close.
just behind is immediately behind
just on schedule is within seconds
just after nine is closer to 9 than after nine.
Many folks would use them interchangeably, but my use is as above.