One of the first decisions you have to make when designing a database is what type of database model to use. There are different types of databases, such as relational, non-relational, or hybrid, that have different strengths and weaknesses when it comes to scalability. Relational databases, such as MySQL or PostgreSQL, use tables and rows to store data and enforce strict rules and relationships between them. They are good for data integrity, consistency, and complex queries, but they can be hard to scale horizontally (adding more servers) and may require more resources and maintenance. Non-relational databases, such as MongoDB or Cassandra, use collections and documents to store data and allow more flexibility and variety in the data structure. They are good for scalability, performance, and availability, but they can be less reliable, secure, and consistent, and may require more application logic and data validation. Hybrid databases, such as Amazon Aurora or Google Cloud Spanner, combine some features of both relational and non-relational databases, such as ACID transactions, SQL support, and distributed storage. They are good for balancing scalability and reliability, but they can be more expensive, complex, and vendor-dependent.