### Introduction In this article, we'll delve into a use case where we can use Redis for query caching, to increase the [RPS](https://en.wikipedia.org/wiki/Web_server#requests_per_second) of our backend service. This article is inspired by [this post](https://redis.io/learn/howtos/solutions/microservices/caching), however instead of using nodejs, we will use Java Spring boot and in addition we will also instrument our code using [OpenTelemetry](https://opentelemetry.io/) and observe the response time using [Jaeger](https://www.jaegertracing.io/). ### Use case Let’s say you are a backend engineer in an e-commerce company and are in charge of product discovery in the homepage. As your company grows, you start selling more products (more data in your database) and more users (more requests) are accessing your e-commerce site. This increase in data size and number of traffic is making your homepage lagging and in turn makes many users complain about your ecommerce website. How can you solve this problem? ### Problem Let’s simulate above use case, below is a simplified diagram to illustrate our system: ![Initial system design](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/gcpzpjbnzuliqzlfzgmq.png) Let’s break down the components of the above system. #### Product DB We use mongodb as our primary database and we will use fashion product [dataset from kaagle](https://www.kaggle.com/datasets/paramaggarwal/fashion-product-images-dataset/data) to populate our data. The dataset contains 44k rows. Below is the example of product data: ``` { "id": "66a1de675d61dc885a0139f1", "gender": "Men", "masterCategory": "Apparel", "subCategory": "Topwear", "articleType": "Shirts", "baseColour": "Navy Blue", "season": "Fall", "year": 2011, "usage": "Casual", "productDisplayName": "Turtle Check Men Navy Blue Shirt" } ``` #### Product Service We will use Spring Boot to build our product service. The product service will provide an endpoint to get list of products by it’s displayName: ``` GET /products/getByDisplayName?displayName={product display name} ``` Here is the relevant code for above endpoint: ``` public List searchProductsByDisplayName(String displayName) { return productRepository.findProductByProductDisplayNameContainingIgnoreCase(displayName); } ``` ``` @Repository public interface ProductRepository extends MongoRepository { @Query("{ 'productDisplayName' : { $regex: ?0, $options: 'i' } }") List findProductByProductDisplayNameContainingIgnoreCase(String productDisplayName); } ``` ``` @GetMapping("/products/getByDisplayName") public ResponseEntity

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Redis for query caching

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