As far as I know, there is no direct equivalent for a procedure in Cassandra. If you need a function in a SELECT, INSERT or UPDATE statement, you can create an UDF, see
CREATE FUNCTION[
^]
On the other hand if you need a block of DML statements, you could use
BATCH[
^]. However, since this is not a stored or named piece of code it's not like a procedure you could call by name. Instead it's more like an anonymous T-SQL block in SQL Server.