online voting problem

The database-server is connected to 2 WebHosts, and 1 LoadBalancer that supports a country-wide election based application, where
users can vote on candidates via internet.

1. There are 5 candidates to vote and a total of 100000 voting users.
2. The database can only hold 1 write concurrently and does not support transactions. If
this value is exceeded, the database responds immediately with an error code=68282.
3. When a user votes it must have an immediate response saying that the vote was
accepted.
4. There may be 100+ users voting at the same time

Problem:
The client is complaining that his users are receiving an error code=68282 while trying to vote.
Elaborate a ​detailed ​solution ​without changing the underlying database​ that can sustain the
demanded load without returning errors to users.

DIAGRAM https://ibb.co/M9fKZ9D