How to store client accesses on the server?

Question

Encryption

Question 1 I
have a server script that connects to various third-party data sources (for example, a website database, a telephony server, a web analytics counter api), selects the necessary data from each source, and does something with them. This script works on krone. We multiply the number of such scripts by 100. Thus, several hundred accesses to different data sources should be stored on the server. If accesses are stored in clear form, when hacked, an attacker gains full access to all data sources. How can you secure the storage of such a large number of accesses on the server while leaving the application architecture workable?
Question 2
A cron script runs on the server that saves some data to the database. This data should only be seen by the client in his browser, neither programmers nor administrators should be able to access it. Those. the data stored in the database must be encrypted, they must be decrypted only in the client's browser. Is it possible to implement such a data storage procedure?