A lot of people get confused about the difference between conducting a systematic review and doing a literature review in a systematic, i.e. organised way.
An official systematic review requires a minimum of two people as, in order to ensure that relevant papers aren't missed and the potential for bias is reduced, you need two reviewers to look at the results and screen them. You may also need the intervention of a third person if there are any conflicts or disagreements as to whether a particular paper should--or should not--be included. This can take up to a year (or more, in some cases) to complete.
A literature review may have been conducted in a systematic, i.e. process-driven, organised way but that doesn't mean that it is a systematic review as that phrase refers to a standard methodology as mentioned above. A literature review only requires one person; the limiting criteria may be more defined so that you may have a restricted date range or language, and it can be conducted in a much shorter timeframe.
There are other types of literature review such as: rapid review, integrative review, meta-analyses which will have similar, but not identical requirements as a systematic literature review and you can find a lot of information on the internet about these.