This article introduces the relevant terms and concepts in the Distributed Cache help documentation to help you better understand the product features.
Instance
An instance is an independently running database environment in Tencent Cloud, serving as the basic unit for users to purchase Distributed Cache, existing as a separate process. A database instance can contain multiple databases created by users. You can create, modify, and delete instances in the console. Instances are independent of each other with resource isolation, and there is no contention for resources such as CPU, memory, or IO between them.
Region
Region (Region) refers to the geographic location of the servers where users purchase Tencent Cloud Distributed Cache instances, and each region is completely independent. When purchasing a Distributed Cache instance, you need to specify the region closest to you to reduce access latency, and changing the region is not supported after purchase. Additionally, Distributed Cache must be used with CVM, and you need to ensure that the cache database and CVM are in the same region.
AZ
An availability zone refers to a physical data center of Tencent Cloud that is independent of other data centers in the same region in terms of power supply and network. Availability zones are interconnected via private network. Network delay is lower within an availability zone. Failures within availability zones are ensured to be isolated from each other (except for major disasters or power failures), so as to prevent fault propagation and ensure that users' businesses continue to provide online services.
Proxy
Proxy server (Proxy) is an independent component in the Tencent Cloud Distributed Cache architecture and does not consume the resources of data shards. By deploying multiple proxy nodes, it can achieve CLB for traffic and failover of the system, thereby enhancing the availability and scalability of the Tencent Cloud Distributed Cache instance.
Replica (Replication)
The replica of Distributed Cache is a data redundancy and high availability solution implemented through the master-replica architecture (Master-Replica). A master node (Master) handles all write operations and asynchronously replicates data to one or more replica nodes (Replica), ensuring that multiple copies of data are stored. When the master node fails, the system automatically triggers failover within seconds, promoting a replica node to the new master node to ensure service continuity.
Shard
The shard of Distributed Cache is a horizontal scaling solution implemented through a distributed cluster (Cluster). In the Tencent Cloud Memory Edition (cluster architecture), a shard is the smallest data unit composed of a group of primary/secondary nodes. The cluster defaults to distributing 16384 hash slots evenly across all shards; after a client Key is calculated by an algorithm, the shard where the corresponding slot resides is responsible for storage and response. By horizontally scaling the number of shards (1-128 shards), slot rebalancing and data migration can be completed online, achieving linear scaling of capacity and QPS.
Tencent Cloud Console
The Tencent Cloud console is the unified web operation panel for Tencent Cloud resources. By logging in to the console, you can visually manage and monitor the full lifecycle of database instances.
Basic Network
A basic network is a public network space used by multiple users. It cannot be segmented. IP addresses are unique, randomly assigned, and cannot be modified.
VPC (Virtual Private Cloud, VPC) is a logically isolated network space customized by you on Tencent Cloud. You can build a logically isolated, user-configured network space for resources such as CVM and cloud database to enhance the security of your cloud resources and meet different use case requirements.
A security group is a virtual firewall that features stateful data packet filtering. It is used to configure the network access control of instances for services such as CVM, CLB, and cloud databases while controlling their outbound and inbound traffic. It is an important means of network security isolation.
Number of Connections
The number of TCP session channels established between the client and the Distributed Cache instance directly reflects the concurrent access pressure. Its upper limit is strictly constrained by the instance's memory specification, and connection pool reuse can significantly improve resource utilization.
Slow query
Slow query refers to a query request that exceeds the specified time range, and the corresponding statement is called a slow query statement. Distributed Cache provides slow query statistics for both data cache nodes and proxy nodes. The information includes the command of the slow query, its occurrence time, request duration, and specific details.
Tag
Tags are used to categorize resources and aggregate them by classification. If your account has multiple cloud database resources with various interconnections, you can use tags to group related or functionally similar resources. During daily Ops or troubleshooting, this enables quick resource search, batch operations, and efficient issue resolution.
A project is the core logical unit of cloud resource management. By aggregating cloud products (such as databases, storage, and computing) into the same space, it enables resource grouping and isolation, unified permission management, and cost allocation accounting, providing infrastructure for team collaboration.
Tencent Cloud CVM (Cloud Virtual Machine, CVM) is a scalable computing service provided by Tencent Cloud. Only by connecting to the private network address automatically assigned to Distributed Cache via CVM can you access the database.
Cloud Access Management (CAM) is a user and permission management system provided by Tencent Cloud, which is designed to help customers securely and finely manage access to Tencent Cloud products and resources.
Data Transfer Service (DTS) is a comprehensive database data transfer service that integrates data migration, synchronization, and subscription. It enables users to complete database migration seamlessly without business interruption.
Distributed Cache instances are integrated with DBbrain's (TencentDB for DBbrain, DBbrain) diagnosis and optimization feature, which monitors and diagnoses database instance exceptions in real time. It automatically generates health reports and provides expert optimization recommendations, helping you comprehensively grasp database performance, quickly troubleshoot issues, and optimize database efficiency promptly.