DB architecture— Which database is best for single key search

I have a very simple database, which consists of two tables:

TabA , idA binary(32) Primarykey NOT NULL
TabB, idB binary(32) Primarykey NOT NULL

Only two simple activities are performing on these tables and they are independent.

Inserting new id to idA in TabA.
Searching TabB idB column for a given value, if not exists insert the given value.

The two tables could grow into billions of records. The data can’t be housekept. Currently the database is in a relational database MS SQL.

Based on the very simple query and flat schema, which type of databases could provide best performance? Search engine? In memory KV? Mapreduce? Thanks in advance!

Hello Frank, sorry to disapoint you, but I cannot give you an answer to such broad question. It really depends on your requirements and personal preferences.
When you will need to help with Toad Data Modeler, I'll be glad to help you, but in this case, I'm not able to do so.

Best regards,