Is it possible for a hash table's load factor to exceed 100%?
The load factor of a hash table is defined as:

$$\lambda = \frac{n}{k}$$

where $n$ is the number of items stored in the table and $k$ is the number of buckets. So the load factor is greater than 1 if there are more entries than buckets.

Storing more than one entry in a bucket is very common. The most familiar example is separate chaining (e.g. a linked list of entries in the bucket), used for in-memory hash tables.

For disk-based hash tables (as found in database servers or some file systems or file management systems), a "bucket" is typically a page (possibly a disk page or a virtual memory page) in size, so for typical use cases, you can easily fit more than one item into it. A scheme such as extendible hashing is typically used to manage buckets in a way that minimises disk traffic.