VOCABULARY
System Design Vocabulary & Glossary
Section titled “System Design Vocabulary & Glossary”Comprehensive Reference for System Design Terms
Section titled “Comprehensive Reference for System Design Terms”ACID (Atomicity, Consistency, Isolation, Durability)
Section titled “ACID (Atomicity, Consistency, Isolation, Durability)”A set of properties of database transactions intended to guarantee data validity despite errors or power failures.
API Gateway
Section titled “API Gateway”A server that acts as a single entry point for a set of microservices, handling request routing, composition, and protocol translation.
AsyncIO
Section titled “AsyncIO”A Python library for writing concurrent code using the async/await syntax, used for I/O-bound operations.
Autoscaling
Section titled “Autoscaling”Automatically adjusting the number of compute resources based on demand.
Availability
Section titled “Availability”The percentage of time a system is operational and accessible when needed.
Backpressure
Section titled “Backpressure”A mechanism where a downstream system signals an upstream system to slow down when it’s unable to keep up with the incoming load.
BASE (Basically Available, Soft state, Eventual consistency)
Section titled “BASE (Basically Available, Soft state, Eventual consistency)”A consistency model used in distributed systems that provides guarantees different from ACID.
Blue-Green Deployment
Section titled “Blue-Green Deployment”A deployment strategy that runs two identical production environments (blue and green) and switches between them for zero-downtime releases.
Bounded Context
Section titled “Bounded Context”In domain-driven design, a conceptual boundary within which a particular domain model is defined and applicable.
Broker
Section titled “Broker”A middleman that handles message routing between producers and consumers.
Bulkhead
Section titled “Bulkhead”A pattern that isolates resources to prevent cascading failures.
CAP Theorem
Section titled “CAP Theorem”States that a distributed system can only provide two of three guarantees: Consistency, Availability, and Partition Tolerance.
CDC (Change Data Capture)
Section titled “CDC (Change Data Capture)”A pattern that identifies and tracks changes to data in a database and propagates those changes to downstream systems.
CDN (Content Delivery Network)
Section titled “CDN (Content Delivery Network)”A geographically distributed network of servers that delivers content to users based on their location.
Circuit Breaker
Section titled “Circuit Breaker”A design pattern that prevents cascading failures by stopping requests to a failing service.
Consistency Models
Section titled “Consistency Models”Rules that define when changes to data become visible to readers (strong, eventual, causal, read-your-writes).
Container
Section titled “Container”A lightweight, standalone executable package that includes everything needed to run software.
CQRS (Command Query Responsibility Segregation)
Section titled “CQRS (Command Query Responsibility Segregation)”A pattern that separates read and write operations into different models.
CRDT (Conflict-free Replicated Data Type)
Section titled “CRDT (Conflict-free Replicated Data Type)”Data structures that can be replicated across multiple nodes and updated independently without coordination.
Database Sharding
Section titled “Database Sharding”Horizontal partitioning of data across multiple databases to distribute load.
Dead Letter Queue (DLQ)
Section titled “Dead Letter Queue (DLQ)”A queue that stores messages that cannot be processed successfully.
Debouncing
Section titled “Debouncing”A technique to limit the rate at which a function fires by waiting for a pause in events.
Distributed System
Section titled “Distributed System”A system where components located on networked computers communicate and coordinate their actions.
DNS (Domain Name System)
Section titled “DNS (Domain Name System)”A hierarchical naming system that translates domain names to IP addresses.
Docker
Section titled “Docker”A platform for developing, shipping, and running applications in containers.
Domain-Driven Design (DDD)
Section titled “Domain-Driven Design (DDD)”An approach to software design that focuses on modeling the domain and business logic.
Downtime
Section titled “Downtime”Period when a system is unavailable or not functioning.
Dynamo
Section titled “Dynamo”Amazon’s proprietary NoSQL database that provides high availability and scalability.
EBS (Elastic Block Store)
Section titled “EBS (Elastic Block Store)”A block storage service provided by AWS for use with EC2 instances.
EDA (Event-Driven Architecture)
Section titled “EDA (Event-Driven Architecture)”An architecture where services communicate through events rather than direct calls.
Edge Computing
Section titled “Edge Computing”Processing data near the source rather than in a centralized data center.
ELK Stack
Section titled “ELK Stack”A combination of Elasticsearch, Logstash, and Kibana for logging and observability.
Event Sourcing
Section titled “Event Sourcing”A pattern where state changes are stored as a sequence of events rather than just the current state.
Eventual Consistency
Section titled “Eventual Consistency”A consistency model where all replicas will eventually become consistent given no new updates.
Failover
Section titled “Failover”Automatic switching to a backup system when the primary system fails.
Fallback
Section titled “Fallback”An alternative response or action when the primary method fails.
Fault Tolerance
Section titled “Fault Tolerance”A system’s ability to continue operating despite component failures.
Federation
Section titled “Federation”Combining multiple separate organizations or systems into a single logical unit.
A high-performance, open-source framework for inter-service communication developed by Google.
GSLB (Global Server Load Balancing)
Section titled “GSLB (Global Server Load Balancing)”Load balancing across multiple geographic locations.
GraphQL
Section titled “GraphQL”A query language for APIs that allows clients to request exactly the data they need.
HA (High Availability)
Section titled “HA (High Availability)”A system design approach that ensures a high level of uptime.
Hash Ring
Section titled “Hash Ring”A data structure that maps data to physical nodes using consistent hashing.
Health Check
Section titled “Health Check”An endpoint or mechanism to verify if a service is functioning correctly.
Horizontal Scaling
Section titled “Horizontal Scaling”Adding more machines to a system to handle increased load.
Hot/Cold/Warm Data
Section titled “Hot/Cold/Warm Data”Data classification based on access frequency (hot = frequent, cold = rare).
Idempotency
Section titled “Idempotency”The property that an operation can be applied multiple times without changing the result beyond the initial application.
Ingress
Section titled “Ingress”Entry point for traffic coming into a cluster from outside.
A service mesh that provides traffic management, security, and observability.
Isolation Level
Section titled “Isolation Level”A setting that determines the degree to which concurrent transactions are isolated from each other.
JWT (JSON Web Token)
Section titled “JWT (JSON Web Token)”A compact, URL-safe token format for securely transmitting claims between parties.
A distributed event streaming platform capable of handling trillions of events per day.
Key-Value Store
Section titled “Key-Value Store”A NoSQL database that stores data as key-value pairs.
Kubernetes
Section titled “Kubernetes”An open-source container orchestration platform for automating deployment and scaling.
K-Factor
Section titled “K-Factor”The average number of recipients who receive a message and forward it to others, used to measure viral growth.
Latency
Section titled “Latency”The time delay between a request and its response.
Leader Election
Section titled “Leader Election”A process by which a cluster of nodes selects one node as the leader.
Load Balancer
Section titled “Load Balancer”A device or software that distributes network traffic across multiple servers.
Logging
Section titled “Logging”The practice of recording events and information during system operation.
LRU (Least Recently Used)
Section titled “LRU (Least Recently Used)”A caching algorithm that evicts the least recently accessed items first.
MapReduce
Section titled “MapReduce”A programming model for processing large data sets in parallel.
Microservices
Section titled “Microservices”An architectural style that structures an application as a collection of loosely coupled services.
Middleware
Section titled “Middleware”Software that acts as a bridge between an operating system or database and applications.
Monitoring
Section titled “Monitoring”The practice of collecting and analyzing system metrics to ensure health and performance.
Multi-Tenancy
Section titled “Multi-Tenancy”A software architecture where a single instance serves multiple customers.
MVP (Minimum Viable Product)
Section titled “MVP (Minimum Viable Product)”A product with just enough features to satisfy early customers and provide feedback for future development.
NAT (Network Address Translation)
Section titled “NAT (Network Address Translation)”A method of remapping IP addresses to preserve IP address space.
N+1 Problem
Section titled “N+1 Problem”A performance anti-pattern where a query is executed for each item in a collection, causing excessive database calls.
A type of database that provides flexible schemas and scales horizontally.
A single server or instance in a distributed system.
OAuth 2.0
Section titled “OAuth 2.0”An authorization framework that enables applications to obtain limited access to user accounts.
OTel (OpenTelemetry)
Section titled “OTel (OpenTelemetry)”An open-source observability framework for generating, collecting, and exporting telemetry data.
Orchestration
Section titled “Orchestration”Automating the arrangement, coordination, and management of complex systems.
P99 Latency
Section titled “P99 Latency”The 99th percentile response time - 99% of requests are faster than this threshold.
Packet Loss
Section titled “Packet Loss”The failure of data packets to reach their destination.
Partition Tolerance
Section titled “Partition Tolerance”A system’s ability to continue operating despite network partitions.
A consensus algorithm for reaching agreement in distributed systems.
Peer-to-Peer (P2P)
Section titled “Peer-to-Peer (P2P)”A distributed network architecture where nodes share resources directly.
Performance
Section titled “Performance”The efficiency of a system in terms of speed, throughput, and resource usage.
Persistence
Section titled “Persistence”The durability of data in storage beyond the lifetime of the process.
Poison Message
Section titled “Poison Message”A message that causes repeated processing failures.
A .NET library that provides resilience and transient-fault-handling.
Pre-warming
Section titled “Pre-warming”Initializing resources before they’re needed to avoid cold starts.
Primary-Replica Replication
Section titled “Primary-Replica Replication”A database replication model where one node is primary and others are replicas.
Pub/Sub (Publish-Subscribe)
Section titled “Pub/Sub (Publish-Subscribe)”A messaging pattern where senders publish messages without knowing the receivers.
Pull-Based Architecture
Section titled “Pull-Based Architecture”A pattern where consumers actively request data from producers rather than receiving pushed updates.
A data structure that holds messages for asynchronous processing.
Quorum
Section titled “Quorum”The minimum number of nodes that must agree for an operation to succeed.
A consensus algorithm designed to be understandable and practical.
Rate Limiting
Section titled “Rate Limiting”Restricting the number of requests a user or service can make in a given time.
RDBMS (Relational Database Management System)
Section titled “RDBMS (Relational Database Management System)”A database system based on the relational model.
Read Replica
Section titled “Read Replica”A copy of a database that serves read requests to reduce load.
An in-memory data structure store used as a database, cache, and message broker.
Replication
Section titled “Replication”Copying data across multiple nodes for redundancy and performance.
REST (Representational State Transfer)
Section titled “REST (Representational State Transfer)”An architectural style for designing networked applications.
Retry Pattern
Section titled “Retry Pattern”Automatically attempting failed operations with potential backoff.
Round Robin
Section titled “Round Robin”A load balancing algorithm that distributes requests sequentially.
Routing
Section titled “Routing”The process of selecting a path for traffic in a network.
Amazon’s Simple Storage Service for object storage.
Scalability
Section titled “Scalability”The ability of a system to handle growing amounts of work.
Sharding
Section titled “Sharding”Horizontal partitioning of data across multiple databases.
Sidecar Pattern
Section titled “Sidecar Pattern”Deploying auxiliary components alongside the main application container.
SLA (Service Level Agreement)
Section titled “SLA (Service Level Agreement)”A commitment between a service provider and client about service standards.
SLO (Service Level Objective)
Section titled “SLO (Service Level Objective)”A target level of reliability for a service.
SQL (Structured Query Language)
Section titled “SQL (Structured Query Language)”A domain-specific language for managing relational databases.
Sticky Session
Section titled “Sticky Session”Routing requests from a user to the same server.
Stream Processing
Section titled “Stream Processing”Processing data in continuous streams rather than batches.
Strong Consistency
Section titled “Strong Consistency”A consistency model where all reads see the most recent write.
Subnet
Section titled “Subnet”A logical subdivision of an IP network.
TCP (Transmission Control Protocol)
Section titled “TCP (Transmission Control Protocol)”A connection-oriented protocol for reliable communication.
Throttling
Section titled “Throttling”Deliberately limiting the rate of requests to prevent overload.
Timeout
Section titled “Timeout”The maximum time to wait for a response before considering a request failed.
TLS (Transport Layer Security)
Section titled “TLS (Transport Layer Security)”A protocol for secure communication over a network.
Traffic Routing
Section titled “Traffic Routing”Directing network traffic to appropriate services or nodes.
Two-Phase Commit (2PC)
Section titled “Two-Phase Commit (2PC)”A protocol for achieving atomic commitment in distributed transactions.
UDP (User Datagram Protocol)
Section titled “UDP (User Datagram Protocol)”A connectionless protocol for fast, unreliable communication.
UI Layer
Section titled “UI Layer”The presentation layer of an application.
Vertical Scaling
Section titled “Vertical Scaling”Adding more resources (CPU, RAM) to an existing machine.
VPC (Virtual Private Cloud)
Section titled “VPC (Virtual Private Cloud)”An isolated virtual network within a cloud provider.
WebSocket
Section titled “WebSocket”A protocol for full-duplex communication over a single TCP connection.
Write-Ahead Logging (WAL)
Section titled “Write-Ahead Logging (WAL)”A technique where changes are logged before being applied.
WAF (Web Application Firewall)
Section titled “WAF (Web Application Firewall)”A security tool that monitors and filters HTTP traffic to protect against web attacks.
WAF (Web Application Firewall)
Section titled “WAF (Web Application Firewall)”A security tool that monitors and filters HTTP traffic to protect against web attacks.
Zookeeper
Section titled “Zookeeper”A coordination service for distributed systems.
Zero Downtime
Section titled “Zero Downtime”The ability to update or maintain a system without interrupting service.
Common Acronyms
Section titled “Common Acronyms”| Acronym | Full Form |
|---|---|
| ACL | Access Control List |
| API | Application Programming Interface |
| ASG | Auto Scaling Group |
| CDC | Change Data Capture |
| CDN | Content Delivery Network |
| CQRS | Command Query Responsibility Segregation |
| CRUD | Create, Read, Update, Delete |
| DAG | Directed Acyclic Graph |
| DB | Database |
| DDoS | Distributed Denial of Service |
| DLQ | Dead Letter Queue |
| DNS | Domain Name System |
| EBS | Elastic Block Store |
| EDA | Event-Driven Architecture |
| ELB | Elastic Load Balancer |
| ELK | Elasticsearch, Logstash, Kibana |
| gRPC | Google Remote Procedure Call |
| HA | High Availability |
| HTTP | Hypertext Transfer Protocol |
| IAM | Identity and Access Management |
| IP | Internet Protocol |
| JSON | JavaScript Object Notation |
| LB | Load Balancer |
| LRU | Least Recently Used |
| MQ | Message Queue |
| MVP | Minimum Viable Product |
| NAT | Network Address Translation |
| NIC | Network Interface Card |
| OTel | OpenTelemetry |
| PKI | Public Key Infrastructure |
| QoS | Quality of Service |
| RBAC | Role-Based Access Control |
| SLA | Service Level Agreement |
| SLO | Service Level Objective |
| SRE | Site Reliability Engineering |
| SSL | Secure Sockets Layer |
| TCP | Transmission Control Protocol |
| TLS | Transport Layer Security |
| TTL | Time To Live |
| VPC | Virtual Private Cloud |
| WAF | Web Application Firewall |
Last Updated: February 2026