Choosing a database engine

Tags: ACG

From time to time, we receive questions about which database engine is better and when to choose SQL over NoSQL. In this article, we’ll explain the difference between these engine types and what factors might influence your decision. This has the potential to be a large and complex discussion or even a full course, but we'll keep this article high-level.

The choice between a NoSQL database vs. a SQL database

This is really a choice that should be driven by how you are planning to use the data.

If it is very structured data where you plan to use table joins and complex data relationships, then you should probably use a SQL (Relational) database. Table joins and efficient complex queries are strengths of databases with well-structured data.

If the data needs to have flexible structures but fairly clear use patterns, then a NoSQL database may be better. NoSQL databases are often the choices for web applications where the ability to accommodate various data structures is a design advantage, and complexity of analysis is not an immediate concern.

There are many types of database engine. Common SQL (Relational) engines include; Aurora, MySQL, MariaDB, Oracle, SQL Server (MS), and PostgreSQL. There are also literally hundreds of NoSQL engines of different types (external site, opens in new tab). AWS promotes their own NoSQL-as-a-service platforms (external site, opens in new tab) (DynamoDB, Neptune, and ElastiCache)—however, you have a wide choice beyond that. All have their relative pros and cons, and as a designer you should choose the database based on the features that you need compared to the cost.

Traditionally, a business would only have one or two different database engines due to the cost of having a team of database admins to administer each engine. With database-as-a-service there is no reason to not mix and match and use the best tool in the right place.

How to manage the database

In the context of AWS, the first choice you need to make is about how you want to manage the database engine. Do you want or need to do it yourself, or would you prefer that AWS managed the hardware, OS, database engine, and fault tolerance so that you can just focus on the data? The latter is database-as-a-service—RDS, DynamoDB, Elasticache, Redshift, Neptune (external site, opens in new tab). You pay a predictable fee based on the size or the number of transactions, and AWS takes responsibility for all the hardware and patching and fault tolerance. The advantages are predictable cost, and a reduced level of infrastructure skill to achieve the same outcome.

The primary disadvantages of this choice are:

  • You must operate within the offered versions and state of the server.
  • You cannot make use of admin-controlled functions, such as Log Shipping or customized disk configurations.
  • You must trust the service that AWS offers.
  • You must trust the compliance certification AWS maintains.

If you have reasons why this is not acceptable, then database-as-a-service is not for you. In this case you can choose to build a database engine on an EC2 instance and have full control of the OS and engine, and if it is justified the choice of dedicated hardware including Bare Metal offerings (external site, opens in new tab).

There is a lot more to databases and the process of choosing the right one for your implementation. If you have an interest in database solutions, we encourage you to read up on industry discussions, then start experimenting with the various types to gain a more intimate understanding of the strengths and weaknesses of each.

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