Cloud database MySQL is the most popular open source database in the world. Users can create a database instance suitable for their application scenarios in a few minutes, quickly put it into production, and pay on demand. As an important part of the open source software combination LAMP (Linux + Apache + MySQL + Perl/PHP/Python), it is widely used in various applications. But many people are confused about the specific differences between traditional databases, cloud database rds and redis. First of all, we need to know:
　　1. What are traditional databases and cloud database rds and redis?
　　Traditional databases are: data sets organized according to a certain data model and stored in secondary storage. This data set has the following characteristics: as little duplication as possible, serving multiple applications of a specific organization in the best way, its data structure is independent of the application using it, and the addition, deletion, modification and query of data are managed and controlled by unified software.
　　Cloud database RDS supports four database engines, namely: MySQL, SQL Server, PostgreSQL and PPAS.
　　Cloud database RDS is a stable, reliable and elastically scalable online database service. Based on FeiTian distributed system and full SSD disk high-performance storage, it supports MySQL, SQL Server, PostgreSQL and PPAS (highly compatible with Oracle) engines, deploys the master-slave architecture by default and provides a full set of solutions in disaster recovery, backup, recovery, monitoring, migration, etc., which completely solves the troubles of database operation and maintenance.
　　Differences between cloud database rds and redis
　　2. Differences between cloud database rds and redis:
　　Cloud database RDS is a relational database, and Redis is a non-relational database
　　Non-relational database: stored by key value, and the structure is unstable. Each tuple can have different fields. This will not be limited to a fixed structure, which can reduce some time and space costs. In this way, in order to obtain different information of users, there is no need to perform multi-table queries like in relational databases. You only need to retrieve the corresponding value according to the key. Relational database: The ACID property of the database reduces the probability of data redundancy and data inconsistency!
　　3. How to choose a MySQL cloud database suitable for your business scenario?
　　1. Select by region and availability zone: Select a region according to the geographical location of you and your target users to improve user access speed. Generally, RDS should be in the same region as the ECS server, so that the network connection efficiency between the application and database deployed in the ECS server is the highest.
　　Availability zone refers to a physical area with independent power and network in the same region to achieve fault isolation. At the same time, MySQL provides the option of multi-availability zone deployment in a specific region, that is, the master node and standby node of the high-availability version are located in different availability zones, thereby providing disaster recovery and high availability across availability zones.
　　2. Choose the right version: MySQL provides three versions of instances: basic version, high-availability version, and financial version.
　　Basic version: Generally used for personal learning or development testing. The defect of the basic version is that the availability is not high, which is suitable for relatively unimportant scenarios, so it is not recommended to use the basic version in a production environment.
　　High availability version: RDS MySQL high availability version adopts a classic high availability architecture with one master and one standby, and uses binlog-based data replication technology to maintain database availability and data consistency. At the same time, the performance of the high availability version can also meet the needs of the business production environment. The configuration uses physical servers and local SSD hard drives to provide the best performance and balanced performance in all aspects.  
　　3. Select the network type, instance specifications, storage space, and purchase duration.
　　The default network type is VPC, i.e. private network. Unless you are an old customer who is already using the classic network, it is recommended to use the VPC private network, which is more flexible and safer. Regarding the purchase duration, we recommend annual and monthly subscriptions. After all, the database supporting the business system will not release resources frequently, and the longer the annual and monthly subscription period, the better the discount, which can help your business applications save a lot of money. But if you are just using it for testing or learning, you can switch to pay-as-you-go in the upper left corner when creating an instance.
　　If you are a jtti user, submit the order and pay. A few minutes later, when you receive SMS and email notifications, the RDS instance is created successfully and can be viewed and used on the management console.
　　For example, in the environment of other manufacturers: if: rds is 8G, the annual and monthly subscription of the main database is 950/month, and the slave database is calculated by volume at about 850/month, rds+reids, generally redis2G is about the same, 180/month, the cost is 950+180. If the database needs more memory, the cost will be much higher if the redis memory is increased in the same proportion. A general main database can currently load 10 read-only instances. However, at this time, it is estimated that the database has to be split.