php - File or Database for searching zip code?

Question

I have a online shopping cart, at checkout user enters his zipcode.

There are 2 payment methods, cash-on-delivery and net-banking. The courier service ships to only certain areas(identified by zipcode). And the allowed list of zipcodes for COD and Net-Banking differ. (length of list = about 2500 for COD, and about 10,000 for latter)

Should I store these lists in database or a flat file?

For database, I will be querying using SELECT, and for file, I can read the entire(or partial) list in array, and then do Binary search on it.

Which one would be faster, considering following points -

1. There is only one courier service now, but in future there will be more, and with different lists of there own. So I need to search in multiple lists.
2. There is mostly read, write would be much less. Also the list should be customisable at later point.

I would have selected Database, but I don't know if it would make things slower, and I don't want to spend time designing database, when a file might be better.

EDIT: Say there are 2 courier companies ABC and DEF.
For file I will have 4 files (say) ABC_COD.txt, ABC_net.txt, DEF_COD.txt, DEF_net.txt. So if a customer goes for COD, I search ABC_COD, if not in there, I search DEF_COD and so on. So ok this seems to be costly, but it is also easily extensible.

Now consider database, I will have a table Allowed_zipcodes, with five columns : zipcode(int/varchar(6)), ABC_COD(boolean), ABC_net(boolean), DEF_COD(boolean), DEF_net(boolean). If the x company offers cod for y code, the corresponding column has true, otherwise false. While this seems good for lookup, adding a company involves a change in schema.

Please consider future changes and design as well.

Answer 1

Database, without any hint of a doubt. More logical, and more scalable.