If you are going to need a significant amount of querying, it would be less ideal to use Redis. This is because your data may be stored in varying styles of specialized data structures, personalized for each type of object for optimum functions. In MongoDB, those very same queries may be simpler to work with because the structure is more consistent across one’s data.
MongoDB offers ease of use and simplicity and features a much shorter learning curve for developers. However, Redis's specific approach requires a lot more effort to learn, but it does provide greater flexibility than MongoDB. A cache layer can also be better implemented through Redis.