Improve the "Under the Hood" parts in docs - thanks to feedback at #458

[seratch]

Summary

This pull request replaces some of the pseudo-code in the "Under the Hood" documents. Refer to #458 to know the context.

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

Merging #461 into master will increase coverage by 0.06%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #461      +/-   ##
============================================
+ Coverage     83.59%   83.65%   +0.06%     
- Complexity     2386     2387       +1     
============================================
  Files           250      250              
  Lines          6442     6442              
  Branches        590      590              
============================================
+ Hits           5385     5389       +4     
+ Misses          694      690       -4     
  Partials        363      363              

Impacted Files	Coverage Δ	Complexity Δ
...pi/methods/metrics/impl/RedisMetricsDatastore.java	89.50% <0.00%> (+2.46%)	38.00% <0.00%> (+1.00%)

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