What technologies to use for the “front end” server to safely validate requests?

Imagine that I have a server made with technologies and programming language that are not secure for some reason, such as legacy versions with known vulnerabilities or anything else that may result in giving a hacker an opportunity to forge an invalid request to access more data or internals of the system.
Now to solve the security problem instead of rewriting the core I would like to place the 2nd server in front of it. It should have libraries to be able to accept simple HTTP requests with headers, parse/generate JSON, do the validation (to ensure it passes valid JSON to the 1st server, i.e. recursively check structure, sizes and encodings) and so be quick, simple and safe enough to make is possible to rarely update it and use any unsafe protocol for easier communication with the 1st server.
What technologies should I use for the 2nd server? What programming language?

Combined DB technologies?

Dear forum – yet another DB decision question. Thanks in advance for any good advice.

So, I am setting up a database for the "media archive" of our company. It includes metadata about (1) print data (such as press clippings, book reviews, marketing documents, books and brochures we publish) and (2) audio-visual data (basically everything with a timeline, such as digitized videos and audio files, DVDs and CDs). So these two build the main data tables and there's a couple of other smaller…

Combined DB technologies?

What web technologies to use for a big site?

What would be the best choice to build a huge website upon? Should I use a framework or build a completely custom platform?

I'm planning to build a very complex learning management site where main functionalities would be: videos, audios, quizzes, chats, payments, messaging, users can interact with each other.

One of the development companies I contacted said they would use WordPress for this, but I'm not so sure it's a good idea.
The website will have a large user base (millions)…

What web technologies to use for a big site?

Technologies involved in a Location Finder

I am a student working on a personal project which is essentially a location finder that will be on a website. I have a data set of over a million addresses and I want to display the closest N locations to a given address or current location.

I would greatly appreciate some examples of the technologies/stack that an experienced developer might use to approach this problem. I know I need to set up a database to query the locations so I’ve tried to import the data to a MySQL server but I’ve been having trouble due to the size of the data set.

From there, I know I need to geocode the database of addresses to get the lat/long values needed to calculate the distances. But would the search algorithm be impractical as it needs to calculate each of over a million entries? Is there a way to optimize that? I was also thinking about a K Nearest Neighbors using a KD Tree with the lat/long values as the axes.

Sorry for the rambling, I have not been involved in a project of this scale and have no idea which technologies I need to use to approach this. I would appreciate some suggestions for how to implement this and some of the various technologies that may be involved. Thank you for your time.

How does bonds in Secure Multi‐Party Lotteries work as described in Bitcoin and Cryptocurrency Technologies book

I have understood the details of it but I have a question related to claiming the bond. We have two parties Alice and Bob and suppose the bond that Alice signs is enter image description here

now if Alice reveals her value X then she will be able to get her bond money back. Suppose if Bob won the lottery then how will he get the money from Alice since she has already reclaimed her bond amount?

What services / technologies are typically used in implementing payment processing?

I’m curious as to how a payment processor and/or automated clearing house are designed and what the stack looks like.

I’m finding it difficult to locate documentation that suggests certain platforms or approaches at a solution level.

I’m particularly curious about the authorization patterns and transaction requests between institutions and payment processors. Is there a standard transaction format? How are these requests and responses received between institutions?