Magento is designed to support thousands of transactions per hour in order for customers to have a seamless online shopping experience. For stores with low traffic, it is recommended to use Magento cloud single-tier architecture to reduce costs in accordance with the actual traffic in the stores.
In single-tier architecture all required components (PHP, DB MySQL, Redis Cache, Cron, NFS, Elastic Search, New Relic for monitoring, Nginx, and so on) are installed on one server. It is easy to use because everything is managed in a single server, but when traffic increases or issues arise with one component, the entire server performance may be affected.
For moderate- to high-traffic stores, it is always recommended to use multi-tier architecture. This will help to solve most performance and security problems, by splitting data and load across multiple servers. Another advantage of multi-tier architecture is its ability to add capacity by increasing the number of nodes during high traffic and reducing it when the traffic becomes normal.
The most common multi-tier architecture pattern is the 3-tier architecture. This pattern divides the infrastructure into three separate layers, with one public and two private layers. Anything in public is publicly accessible, but data in the private layers are only accessible from internal networks (for example store admin, DB, and so on). Multi-tier architecture in the cloud also helps by splitting network access across different zones. Even if one zone is down, the customer traffic will be routed to another available zone.