HERE Map Tile 2
HERE Map Tile v2 Developer's Guide

Load Balancing and URLs

The servers that process requests against the HERE Map Tile v2 resources are distributed for optimized load balancing. Clients can use this feature to improve response times, especially when submitting multiple requests simultaneously, by using URL prefixes (1 - 4). The numeric prefix must be the first part of the request URL after http://.

There are different ways to use this mechanism. No method is enforced from the server, although the method you use should ensure that your requests are distributed among the different prefixes; do not use only one numeric prefix.

We propose the following methods:
• Choose the prefix randomly.
• Choose the prefix depending on the parity of the row and column number:  1 – when both the row and the column number are even 2 – when the row number is even, the column number is odd 3 – when the row number is odd, the column number is even 4 – when both the row and the column number are odd
• Use a simple formula such as:
1 + ((row_number + column_number) % 4)
In this formula, % indicates modulo division.