Generating unique orderId and customerId does not guarantee 100% uniqueness, but it is possible to overlook the problem given the low probability

[Fernando-Granato]

For the generation of the unique orderId and customerId for NPG I thought to proceed from the timestamp in milliseconds by concatenating random way N characters between URI safe alphanumeric values.

I ruled out concurrency problems in generating the two ids in the same millisecond through a probability calculation described as follows.

Consider the length of the timestamp string in milliseconds = 13
So the random string to be generated will be 18 (maximum length of the unique id) - 13 = 5 characters
Suppose we have 2000 RPS on the service (very large number of requests) so 2 requests per millisecond.
The number of alphanumeric characters used to generate the random string is 65.

const val ALPHANUMERICS: String =
           "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-._"
     

We calculate all possible combinations $65^5 = 1 160 290 625$.

At this point $1 / 1 160 290 625 = 0.000000000861853$ (negligible probability of collision).