How to optimize and reduce the PHP code?

Good evening. I have the following code:
The first part of the code up to 47 rows to build the array $result with the SKU of the product catalog.
The second part of the code after 47 lines is iterating through the array $result and displays detailed info about each product.
Goods there are about 20,000 pieces.
Immediately there was a problem. If you try to run this code the script starts feeling and in the end gets an error 504 Gateway Timeout
The page, which gets this error -
As you can more or less optimize the code and reduce the loading time of the script?
March 20th 20 at 11:47
2 answers
March 20th 20 at 11:49
Not to make the Assembly of data on each request, to pay pre-collected data, and a demon somewhere in the background to update this information after some period of time.
March 20th 20 at 11:51
What is written in the answer above, plus

Find out if the service the ability to request multiple records.
It's possible to cache the information.

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