Cost-Effective Image Management: Maximizing Efficiency Through Network Image Caching in Mobile Apps
Tags: caching, mobile
Published: 2024-06-11 03:02:51

In today's mobile app landscape, user experience is paramount, with performance and cost efficiency playing pivotal roles in app success. One often-overlooked aspect that significantly impacts both these factors is the management of images. Incorporating image caching strategies can not only enhance app performance by reducing load times but also contribute to significant cost savings in data usage and server resources. 

In this article, we delve into the benefits of caching network images in mobile app development, exploring how this optimization technique can positively influence both user satisfaction and the bottom line.

---

Mobile apps can utilize various caching techniques to enhance performance and reduce load times. Here are some common caching methods:

**Web Caching**: This technique involves storing static content, like images and JavaScript files, in the browser’s cache. By doing so, it significantly reduces the time required for an app to load, as these resources do not need to be repeatedly fetched from the server.

**Data Caching**: This approach stores frequently accessed data, such as user profiles or product catalogs, locally on the device. It minimizes the need for constant database queries, thereby speeding up data retrieval and enhancing the app’s responsiveness.

**Application Caching**: This method caches data generated by the app itself, such as the results of computations or rendered views. It is particularly beneficial for apps that perform intensive calculations or render complex interfaces, as it reduces processing time and improves overall performance.


Several advanced caching strategies can further enhance the performance of mobile apps. These advanced methods include:

- **Cache-Aside**: This strategy involves storing data in both the cache and the database. When the app needs to access a specific piece of data, it first checks the cache. If the data is not found there, the app queries the database and then stores the retrieved data in the cache for future access. This approach reduces the number of database queries, thereby improving performance.

- **Cache Invalidation**: To ensure that the cache always contains the most up-to-date data, this strategy invalidates the cache whenever data in the database is updated. When the next request for this data is made, it is fetched directly from the database and the cache is updated accordingly. This method helps prevent stale data from being served to users.

- **Distributed Caching**: This strategy involves storing cached data in multiple locations, such as across different servers or in the cloud. By distributing the cache, the load on any single server is reduced, which enhances performance and reliability, particularly in high-traffic scenarios.

The optimal caching strategy for a specific mobile app depends on the app’s unique requirements. However, by implementing advanced caching techniques, mobile app developers can greatly enhance their app’s performance.

**Why is it important to cache images?**

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/2f1q02ct4b6o7elhkngd.png)

The screenshot above shows detailed network image requests from CloudFront. It is evident that these static image objects have tens of thousands of requests, with a total bandwidth usage exceeding 1GB.

This scenario represents cost inefficiency, as these images could be stored directly within the application files. However, storing images within the application increases its download and installed size, which can be a concern for users who are sensitive to app size.

Storing images on the server and making the app request them introduces new challenges, including increased loading times and high bandwidth usage, as illustrated in the image above.

By implementing a caching strategy, we can reduce network requests, which in turn helps lower costs such as:

**Cost Inefficiency of Network Requests**
The image illustrates a high number of requests and significant bandwidth usage for static images. When these images are repeatedly requested from the server, it not only increases the load on the server but also results in higher operational costs due to the increased data transfer

**Impact of Embedding Images in the App**
One potential solution to avoid network requests is embedding these images directly in the app. However, this leads to a substantial increase in the app's size, affecting both the download size and the installed footprint. This can be a significant drawback for users with limited storage or data plans, potentially leading to reduced app adoption.

**Challenges with Server-Stored Images**
When images are stored on a server and the app fetches them dynamically, it introduces several issues:

  1. Loading Time: Every time an image is requested, the app must wait for the server response, which can lead to delays in image rendering, affecting user experience.

  2. High Bandwidth Usage: As shown in the CloudFront data, frequent requests for images consume a large amount of bandwidth, increasing operational costs.

**Benefits of Implementing Caching Strategy**
Implementing a caching strategy can mitigate these issues effectively:

  1. Reduced Network Requests: By caching images locally on the user's device after the first download, subsequent requests for the same images can be served from the local cache, significantly reducing the number of server requests.

  2. Cost Reduction: With fewer network requests, there is less data transfer, leading to lower bandwidth costs.

  3. Improved User Experience: Cached images load faster since they are served from local storage rather than fetched from a remote server, resulting in a smoother and more responsive app experience.

---

We only need these two plugins;
- [Cached Network Image](https://pub.dev/packages/cached_network_image)
- [Flutter Cache Manager](https://pub.dev/packages/flutter_cache_manager)

Many of us are already familiar with those packages, as it is a popular choice for displaying images in Flutter applications that implement caching strategies.

Cached Network Image is a flutter library to show images from the internet and keep them in the cache directory.

```
CachedNetworkImage(
  imageUrl: src,
  fit: fit,
  height: height,
  width: width
)
```

This is a common use case for CachedNetworkImage, where cached network images are stored and retrieved using the flutter_cache_manager.

Now, we can customize this widget by adding a CacheManager to manage its configuration. 

```
CachedNetworkImage(
  imageUrl: src,
  fit: fit,
  height: height,
  width: width,
  cacheManager: CacheManager( // Cache Manager Config
    Config(
      src,
      stalePeriod: const Duration(hours: 1),
    ),
  ),
)
```
The configuration object specifies the source URL (src) and the stale period (stalePeriod) for the cached image. This allows for more precise control over how images are cached, ensuring that the app retrieves the most up-to-date images when needed while still benefiting from the performance enhancements of caching.

In this case, the stale period is set to 1 hour, meaning that the image will be considered stale and fetched from the network after 1 hour.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/e11xohtq6gnqfwxhfvf0.jpg)

Here's an explanation of how CacheNetworkManager and CacheManager work:

1. CacheNetworkImage is a widget used to display an image from a URL source in the Flutter app UI.

2. When CacheNetworkImage is requested to display an image from a specific URL, it asks for the image from CacheManager.

3. CacheManager is a package used to manage image caching in the Flutter app.

4. CacheManager checks if the requested image is available in the local cache or not.

5. If the image is available in the cache, CacheManager returns the image from the cache to CacheNetworkImage.

6. If the image is not available in the cache, CacheManager downloads the image from the requested URL and stores it in the local cache.

7. After downloading and storing the image in the cache, CacheManager returns the image to CacheNetworkImage.

8. CacheNetworkImage then displays the received image from CacheManager in the Flutter app UI.


By using CacheNetworkImage and CacheManager, the Flutter app can display images from URLs efficiently by utilizing the local cache. This helps reduce bandwidth and image loading time, especially if the same image is requested repeatedly. Also offers several benefits for application performance, network efficiency, and cost-effective bandwidth usage:


**Performance Improvement**
By caching images locally on the device, CachedNetworkImage reduces the time it takes to load images after the first download. This leads to faster image rendering and a smoother user experience, especially when the same images are used repeatedly within the app.

**Network Efficiency**
With a CacheManager configured, the app can manage how often it fetches images from the network. The stalePeriod parameter ensures that images are only re-downloaded after a specified period, minimizing unnecessary network requests. This reduces the load on the server and helps prevent network congestion.

**Cost-Effective Bandwidth Usage**
Reducing the number of image downloads translates directly into lower data usage. For users on metered connections, this means less data consumption and potential cost savings. For the app provider, it means reduced bandwidth costs, as fewer network requests are made to fetch the same resources.


Implementing a caching strategy for static images is a cost-effective solution that balances the need for a smaller app size with the demand for quick and efficient image loading. This approach not only reduces operational costs but also enhances the overall user experience by decreasing load times and conserving bandwidth.