The Role of Flexibility in Scalable Architecture
Building Flexible Software Architectures: Principles and Strategies
In my previous article, I discussed why adopting a scalable architecture is necessary to enhance business acceleration. In this article I will delve deeper into the concept of scalable software architecture and in particular Flexibility as one important aspect of a scalable architecture.
Flexibility - one angle of Software Architecture Scalability
Scalable software architecture is designed to expand seamlessly with the growth of a business. It's agile, adaptable, and has the capacity to accommodate dynamic changes.
When discussing scalable architecture, there are multiple angles to consider:
Functional scalability, often referred to as Flexibility, is one aspect of software scalability. It highlights a system's ability to adjust to changing requirements, allowing for the addition of features, fixing bugs, or updating the system without significant effort or requiring a complete redesign.
Load scalability views scalability from a different perspective. It's about the system's ability to handle increased traffic without compromising performance efficiency. A scalable system can manage high-peak traffic, ensuring reliable and high-performance operation at optimal costs.
Data scalability is similar to load scalability, but the focus here is on the system's efficiency in managing growing volumes of data. It becomes crucial how optimally the software processes, stores, archives, or integrates scalable data storage solutions to maintain optimal performance.
What do we expect from a Flexible Software Architecture
If a flexible architecture enables fast and effective implementation of system changes into production, it should embody a high degree of:
Maintainability - Simplifying updates and issue resolution within the system.
Testability - Streamlining the testing process post-update implementation.
Deployability - Ensuring rapid deployment of tested changes into production.
These three elements are crucial stages in the process of implementing changes in a system and transitioning it to production. A flexible architecture should support each of these areas.
How to achieve Flexible Architecture
So, what principles do we need to follow to build an architecture that is flexible and supports easy maintenance, testing, and deployment?
1. Build the system in well-defined modules
At the heart of a Flexible Architecture lies Modularity.
Modularity entails a software system characterized by a clearly defined structure. It involves constructing software using smaller, well-defined modules (or components) that have minimal interaction with each other. These modules adhere to the same modular approach internally, consisting of submodules with an optimal number of dependencies.
An analogy for modular architecture is a library, where bookshelves represent modules. In a well-organised library, each bookshelf serves a specific genre, easily managed independently. Additionally, each bookshelf is further divided into categories based on titles, making it effortless for visitors to find a specific book. This stands in stark contrast to a disorganised library, where finding the series of your favourite books can be nearly impossible, and chaos ensues when multiple people search simultaneously.
There are a few key principles of a modular architecture:
Principle 1: Single responsibility modules. Each module is dedicated to a specific function; it should have a single responsibility. When a module's purpose isn't clearly defined, it tends to accumulate unrelated logoc over time, growing into a large module that becomes a maintenance bottleneck.
Principle 2: Clear interface hides implementation details. Modules maintain well-defined interfaces for communicating with other components. This ensures that a module's code interacts solely through its interface, encapsulating the implementation details. In the figure above, Module A communicates with the external system through a dedicated submodule. This setup enables seamless replacement of the external system by updating only the relevant submodule, minimising disruptions in the rest of the system.
Principle 3: Minimising dependencies. Modular design aims to minimise connections between components. Fewer dependencies lead to decoupled modules, making it easier to replace one with less impact on the system. This emphasis on minimising dependencies is particularly vital for higher-level modules, although lower-level submodules may accommodate more intricate connections.
Modular architecture facilitates Maintainability
In a modular system, implementing small updates becomes easier, as developers can quickly pinpoint where a change should be made within the well-defined modules. The fix remains encapsulated, preventing changes from affecting the entire system.
Expanding the system with new functionality is also manageable within the well-defined modular system framework, where each component has its designated place.
Additionally, replacing a component is more manageable compared to a non-modular system because it only affects a small portion of the codebase. This flexibility enables seamless changes to the system.
2. From Modules to Deployable Units
Before we proceed further, let's delve into the concept of a deployable unit and monolithic architecture.
A deployable unit refers to a single piece of executable code.
In a monolithic architecture, the entire system is contained within a single deployable unit, commonly known as a monolith.
While discussing modularity, we didn't explicitly mention that modules are independently executable units. Consequently, a system with a modular architecture can still be a monolith - a modular monolith. In such cases, the entire system functions as a single executable component, with a well-organised codebase structured into software modules.
A monolithic architecture is simple and straightforward, making it a suitable choice for smaller systems.
However, it does come with limitations. As the system and the team responsible for its maintenance grow in size, sustaining it as a monolith becomes progressively challenging.
Smaller deployable units enhance Deployability
Monolithic architecture presents limitations in deployability. Even minor modifications in the system necessitate deploying the entire system, posing obstacles for the entire team. This leads to code freezes, lengthy and intricate testing procedures, and prolonged deployment cycles spanning weeks.
The concept of frequent deployments becomes unfeasible, and introducing new changes for customers on a regular basis becomes both risky and unfavorable for the business. This often results in delayed implementation of new features or bug fixes, leaving them in production for weeks.
To address these challenges, segmenting the application into distinct deployable components (or services) proves advantageous.
Applications with smaller deployable units experience quicker time to market and increased agility. Deployment processes are shorter, risks are smaller, and customers can benefit from more frequent code updates.
Smaller deployable units promotes Testability
Large monolithic applications also add complexity to the testing process. Even if the monolithic application has a comprehensive suite of regression tests, implementing a change and redeploying the entire application entails executing an extensive list of tests, making the process slow and often frustrating for the engineering team.
Partitioning the monolith into smaller deployable units, when done correctly, can significantly enhance testability. When a change is made only in a smaller deployable component, the testing scope becomes more focused, and testing becomes faster. Additionally, maintaining unit tests for smaller deployable units is considerably easier.
How to approach the decomposition process
However, the process of decomposing a monolithic structure into separate components must be approached with careful consideration and a clear rationale.
Companies often aspire to transition to a micro-services architecture (where the system is divided into very small deployable units, each with its dedicated data storage), expecting direct benefits. However, if not executed correctly, this intricate renovation process can significantly increase the existing challenges.
The most daunting scenarios arise when attempting to prematurely separate small services from a large monolith. Not only is the separation itself challenging, but replacing software code dependencies within the monolith with (network) dependencies between deployable units can significantly impact the system's performance efficiency.
To transition from a monolithic to a service-oriented architecture, the initial step is to modularise the architecture and then gradually isolate the most independent modules as deployable units.
Final thoughts
The path toward scalable and flexible software architecture is a strategic imperative for businesses pursuing agility and growth.
It's essential to recognise the trade-offs and challenges that are part of this journey. Software architecture is defined by these trade-offs. It's crucial to carefully weigh the pros and cons and find the right balance. Achieving perfection in every aspect is impossible.
This blog is part of the series on Scalable Software Architecture. Below, you'll find an index of the articles in this series:
The Software Development Reality: The Need for Scalable Architecture
Empowering Growth: The Importance of Performant Scalable Architecture
How to Establish Architecture Principles for Successful Scaling
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