The Importance of Understanding Availability Tiers:
Safeguarding Business Continuity

In today’s digital age, businesses heavily rely on applications and software to function efficiently and serve their customers. From online banking to e-commerce platforms, applications have become the backbone of many sectors. However, with this reliance comes the risk of potential IT incidents that can disrupt business operations. This is where the concept of tiered availability becomes crucial. Understanding the Tiers of Service Availability, the tiered availability model is a hierarchical structure that categorizes applications based on their criticality to business operations.

Understanding the Tiers of Service Availability 

The tiered availability model is a hierarchical structure that categorises applications based on their criticality to business operations. Let’s break down the tiers: 

Tier 0: This is the highest level of criticality. Often referred to as the “crown jewels” of a business, these applications demand immediate attention when issues arise. Any downtime or malfunction can have catastrophic consequences for the company. Consider a bank’s payment system – if it goes down, customers can’t make transactions, leading to a loss of trust and potential financial repercussions. 

Tier 1: The second-highest level of criticality. Whilst these applications are crucial, they have more lenient service levels compared to Tier 0. They are essential but can tolerate short periods of downtime without causing significant business disruption, especially if planned in advance.  However, lengthy downtime will impact revenue and/or the company’s ability to operate. 

Tier 2: These applications can endure some downtime. A large portion of a company’s applications might fall into this category. Whilst they are important, their temporary unavailability won’t necessarily halt business operations.  Downtime is annoying but does not cause significant material loss.  For example, staff can’t make holiday requests – this can easily be tolerated even for a couple of hours. 

Tier 3: The lowest level of criticality. These are miscellaneous applications that, whilst useful, don’t play a central role in the company’s primary operations. 

The "Out of Business" Scenario 

Bank Scenario:  

Imagine a scenario where a bank’s primary application, responsible for facilitating client payments, stops working. Not only would this inconvenience customers, but it could also lead to significant financial losses and tarnish the bank’s reputation. Such a scenario could potentially put the bank out of business. 

This is precisely why Tier 0 support is vital. For businesses with hundreds of applications, identifying and prioritising those that are mission-critical ensures that they receive the attention and resources they deserve. 

Retail Scenario: 

Consider a retail company that relies on an e-commerce platform to sell its products. The e-commerce platform is categorized as Tier 1, as it is essential to the company’s operations but can tolerate short periods of downtime without causing significant business disruption. However, if the platform goes down during a busy shopping season, such as Black Friday, it could lead to a loss of sales and customer trust. In this scenario, the company would need to have a plan in place to quickly resolve any issues that arise with the platform. 

Manufacturing Scenario: 

Imagine a large-scale automotive manufacturer whose entire production line is heavily automated and synchronized through a central control system. This system is not just a part of the manufacturing process; it is the heart of it, managing everything from assembly line robotics to supply chain logistics and real-time quality control. We categorize this system as Tier 0, as it is absolutely critical to the company’s operations. 

One day, this central control system experiences a catastrophic failure. Instantly, the entire production line grinds to a halt. Assembly robots freeze, supply chain coordination is lost, and real-time monitoring of production quality is disrupted. This isn’t just a minor inconvenience; it’s a complete operational shutdown. Every minute the system is down, the company incurs massive financial losses due to halted production, potential contractual penalties, and a backlog of orders. 

Moreover, the ripple effect of this shutdown is felt across the supply chain, affecting numerous suppliers and dealers. The company’s reputation for reliability is at stake, and there’s a real risk of losing long-term contracts to competitors. 

In this scenario, the company must have an immediate and effective response plan. This might include resilient architecture, a 24×7 support team, a robust disaster recovery strategy, and an automated failover strategy that can take over with minimal downtime. The company’s survival depends on how quickly and efficiently it can respond to such a critical system failure. 

The Value of Investing in the right Availability Tier 

What gets you to the right availability tier?  It’s a combination of things:  infrastructure, design, processes, support.  The higher the availability, the more it will cost you to run your application.   

Tier 0 will likely involve your application running active-active in multiple cloud regions, perhaps spread over multiple availability zones within those regions as well.  Your design will carefully consider state, perhaps replicating your data across multiple regions before you consider it “committed” in order to reach your Recovery Point Objective.  You might need dedicated support teams on hand 24×7 in case things go wrong.  This all means more scale, more hardware, more people and more cost. 

Alternatively, a Tier 2 application might be a simple application running in a single region on the most basic settings – and accepting the availability that comes with it.  If something happens overnight, or at the weekend, and someone has a look at it on the next working day – that might be fine.  The costs will reflect this light-touch. 

It’s important that you get your availability tier right.  Cut corners on mission-critical apps and you have high risks.  Overengineer simple applications and you’re going to be uncompetitive on cost.  It’s all about finding the right balance for you. 

Companies like 345 Technology emphasise the importance of getting your availability tiers correct – for a reason.  Customers often come to us when they are struggling to reach their Tier 0 and Tier 1 availability targets.  For these customers, investing in top-tier availability for mission-critical applications is not just a luxury; it’s a necessity. Here’s why: 

Business Continuity: Ensuring that Tier 0 applications are always up and running minimises the risk of business disruptions.  For some of the major banks and national brand retailers we work with, they simply have to get this right. 

Customer Trust: Customers rely on businesses to provide consistent and reliable services. Any downtime can erode that trust, leading to lost clientele and revenue.  Again, in the modern business environment where switching is easier than ever, the customer exodus can be very fast when trust is lost. 

Financial Implications: Downtime, especially for Tier 0 applications, can result in significant financial losses.  For retailers, this is lost sales that have gone elsewhere.  For banks this might be significant penalties from the regulator. 

Reputation Management: In a world where news travels fast, any significant IT incident can harm a company’s reputation. Investing in the right availability tiers helps mitigate such risks. 


In conclusion, the tiered availability model provides businesses with a clear framework to prioritise their IT resources. For large businesses, especially those with numerous applications, understanding the criticality of each application is paramount. Investing in Tier 0 infrastructure, design and support, like that offered by 345 Technology, ensures that mission-critical applications receive the attention they deserve, safeguarding businesses from potential “out of business” IT incidents. 

Further reading