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The “traditional” definition of three-tiered architecture comprises of three layers, they are:
- A presentation layer
- An application layer
- A database layer
True three-tiered architecture allows you to scale or migrate any individual layer without affecting the other two layers. In others words, you can change any layer without changing a single line of code in the other two layers.
If you look at it, it's a wonderful idea because it facilitates you to plug and play any component cleanly and seamlessly. The same can be said for the web application layer where the development of the HTTP protocol actually created the web application layer. It is completely dissociated from the application and the database layers. Since it specifies the protocol, the entire process of HTTP separation of web and app server tiers becomes easy and feasible.
However, if you look at it pragmatically, you’ll notice that your application and database layers are not even close to being separate entities. They are so well intertwined that you simply cannot make any changes to one infrastructure without affecting the other.
The harmony of applications and database
Applications and databases are always inextricably linked. Database vendors, unlike “clean” HTTP, introduced proprietary extensions and implementations of the SQL language. As a result of the SQL language's development, any persistence-related application change had to be reflected in the database, and vice versa.
Anything that occurred on one tier had to be reflected on the other. When both systems were run on the same server, the speed of the processing was accelerated because the data didn't have to move as far.
Breaking up is a hard task
Cloud computing has altered the dynamics completely, promising on-demand scalability — except that it isn't happening.
Still it is almost impossible to separate the application server from the database. A small change to one tier can have adverse effects on the way the other two tiers communicate. For instance, a change in the database may “disrupt” connectivity in the application. So, when the application calls for a ‘purchase order number, the SQL is set up to serve that specific piece of data. However, an update to the accounting database changes the ‘purchase order number’ to a ‘work order number’, making it inaccessible to the application.
Bottom line, it requires extensive static analysis of code-to-database to find all the couplings before anything can be changed.
Falling short of the 3rd Tier
The truth is that companies are finding various workarounds during the cloud transition instead of directly addressing the coupling problems. They divide their efforts, running on-premises and cloud databases parallelly as they gradually transition functionality. They migrate old data to the cloud database and write to both databases. If no issues occur, and both databases are in sync, they then turn over read queries.
Which is fine, except:
- It is complicated to partially roll over data functionality if organizations cannot efficiently read, route, and write traffic to specific databases.
- When things go wrong, DBAs cannot be able to roll back fast enough. Since data and application logic are often intertwined, moving to a different database during a failover without relevant code changes can result in application errors. This makes migrations risky for organizations that can't change or modify their data infrastructure in real-time.
- Successful DB migrations require deep monitoring and centralized login capabilities. If IT teams lack the necessary transparency during database migration, such as having no insights into performance or clear audit trial accountability, it is very likely that the transition will be unsuccessful.
- The SQL-based tight coupling between databases and applications necessitates extensive code changes in the applications each time the underlying data storage is changed, making cloud migration more risky.
The way to achieve a true 3-Tiered architecture
The secret to this is load balancing, which plays a crucial role in the decoupling process. Load balancing serves as an “automatic” translator. It works as a middle layer and keeps the communications channels open between the database and the application, but at the same time, it effectively and completely bypasses the tight coupling, allowing each to seamlessly scale or migrate as needed.
This process simplifies the ability to manage the database-application couplings without causing any harm to either. With true 3-tiered architecture, your database can now quickly and fluidly “communicate” with multiple applications, and your applications can in return easily communicate with multiple databases.
With database load balancing in the fold, each challenge can be addressed to truly benefit from cloud scaling. Database load balancing improves task distribution across multiple servers. Intermediary control planes, which convert SQL commands into cloud-active operations without modifying a single line of code, will make migration easier. Database load balancing decouples programs from their storage, simplifies operations, and lowers TCO significantly.
The end result is - safe migrations with zero downtime, with the ability to switch reads to the cloud server and switch writes at any time you want.
After migration, it is important to keep the database load balancer in place. This provides long-term stability and scalability, delivering zero downtime during maintenance. It also helps in significantly reducing the risk of unplanned outages.
Database Load Balancing offerings
Allows developers to direct an application to a single connection and help them communicate with data without having to worry about the database infrastructure.
Understands several SQL dialects, making way for complex traffic routing without compromising transactions, and lowering costs by reducing or eliminating downtime.
Analyzes traffic spikes to distribute resources accordingly. Minimizes the effect on end-users, ensuring data availability and accessibility for mission-critical business applications.
Allows for a secure and fast rollback of migration if a database encounters any problems. The DBAs can set up failover requirements to reroute traffic away from faulty database nodes without causing application errors.
Managing operations with Load balancing is just as easy:
- Enables consolidation of thousands of schemas on a single cloud database cluster, leading to simplified operations and reduced costs, thus delivering 10x the performance at a tenth of the price.
- Release apps and achieve cost savings, revenue increments by efficiently avoiding downtime; reduced development time and improved website performance.
- Real-time visibility, with quick detection and response to problem queries.
- Transform the two tiers and truly follow three-tier architecture.
- Scale to thousands of transactions per second. Seamlessly migrate to larger instance sizes, or effectively use read replicas at scale.
- Effective read and write traffic balancing to significantly increase overall database throughput.
- Consolidated database analytics in a single framework for smarter, more flexible decision-making that saves time and money.
