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I am writing a Java application following the MVC pattern, abstract enough to allow the backend to connect to an Sql and a NoSql database. I have 4 model classes and 4 DAO interfaces. Each DAO is implemented in two ways, one for sql and one for mongodb. I want to add a Transaction Manager to execute database operations in atomic transactions: the problem is that these operations involve a variable number of DAOs and I don't know how to implement the Manager with more than one Dao. I'm not using Spring and I'm not willing to add it.

I've had the following ideas but each one has something I'm not sure about:

• Make interfaces `MyDao_X` extend another interface `GenericDao` and use the last one in TransactionCode. This way I wouldn't know which Dao to instantiate in `TransactionManagerMysql`
• Extend Function to be an N-Function which can accept N inputs and produce an output. In this case N = 4, so I could always instantiate all the DAOs. Here the doubts are the following: I don't know how to do and I'm following TDD so I should figure out how to test this extension. Moreover, it doesn't seem very efficient to me to instantiate 4 Dao every time just because I don't know how many or the type I need. Additionally, if the number of Dao changes over time, I would be forced to modify all the functions in Service Layer to adapt the number of inputs to lambdas

Recently I came across a well-known design problem. 'Tiny URL'

What I found was people vouching for NoSQL DBS such as DynamoDB or Cassandra. I've been reading about Cassandra for a couple of days, and I want to design my solution around this DB for this specific problem.

1. What would be the table definition? If I choose the following table definition:

Create table UrlMap(tiny_url text PRIMARY KEY, url text);

Wouldn't this result in a lot of partitions? since my partition key can take on around 68B values (using 6 char base64 strings)

Would that somehow affect the overall read/write performance? If so, what would be a better model to define the table.

My doucments:

Is it possible to use EF Core 6 in combination with a MongoDb? From what I'v gathered online, I could only find answers from a few years ago that say that it's still not possible, but nothing that was published recently. There is also better support for the Azure Cosmos Db which is also a NoSql database, so maybe I could use that to communicate with a MongoDb?

If it's still not possible, what other approach should I use?

I have collection with some documents. Sometimes i need to move certain document to another collection (aka archive) and i also need to add archiving time to it. Now i do it in two queries, but want to reduce to one.

Due to lack of experiense in NoSQL, it`s hard to me to make any assumption, so i am asking for help.

I'm at the beginning of starting a project for learning backend development with a bit of frontend development. For that, I wanted to create a project around cooking recipes. The plan was to create an admin REST API that would be later used by a custom CMS to create, edit, delete,... recipes and a public api for a mobile app where your users can discover cooking recipes. Simplicity wise, I thought about choosing Mongodb as the database. While creating a Mongodb schema, I came up with this idea:

• Three main collections

I am confused in choosing database service for my flutter application. I started using firebase but as it is based on NoSQL , But if i am getting the need for rows and columns for my data which backend service should i use!.

How to return for loop values without any html template in flask , in the below code I need to get all jokes values having multiple jokes route but i want them to be displayed as a list one below the other , currently the output I am getting is as a whole list item , I am aware i can use jinja for this but here i want to do without creating any html page

Hi I'm learning the feature of NoSQL database from system design perspective and also read that a lot of big companies use a sharded RDBMS instead of those nosql databases to save their data.

Does this make that the only advantage of NoSQL data (Cassandra/MongoDB) is because it's an off-the shelf distributed solution and cheap to maintain?