[OSM-dev] About rendering and editing databases

[Nick Hill]

Immanuel Scholz wrote:
>>Should rendering DB be the same as editing DB? Experience (wikipedia)
>>says no, doesn't it...

> I'd say we should have many rendering engines on top of many replica
> databases and one main database (with editing capabilities and a simple
> rendering). This way, most (if not all) read requests will draw from the
> backuped databases while it is still possible to verify your latest change
> in the main database.

If all databases are the same, then this can be achieved easily through 
database replication. The replica databases will be updated almost 
immediately.

As the project grows, we will need a database farm.

Ultimately, we should have one server which never serves selects, only 
inserts, to keep editing smooth. It is much more costly for inserts to 
fail than for selects to be slow or fail.