Latency

What Is Latency?

Latency is the time delay between the initiation and completion of a process. In networked systems and AI infrastructure, it represents the time required for data to travel from one point to another—most commonly measured as the delay between a user’s action and the system’s response. Typically quantified in milliseconds (ms), latency represents the “lag” users perceive during interactions with web applications, APIs, or AI-powered services.

Latency fundamentally impacts every aspect of digital system performance, from user satisfaction to business outcomes. In high-frequency trading, a single millisecond can mean profit or loss. In autonomous vehicles, delays pose safety risks. In conversational AI, high latency degrades the naturalness of interactions, making responses feel slow and robotic.

Types of Latency

Network Latency

Time for data to travel over a network from sender to receiver. Affected by physical distance, transmission medium quality, number of network hops, and congestion levels. Fiber optic connections provide lowest network latency, while satellite connections exhibit highest due to vast distances signals must traverse.

Retrieval Latency

Time taken for a system (e.g., AI model) to fetch relevant data from storage or knowledge base after receiving a query. Critical in RAG (Retrieval Augmented Generation) systems where document retrieval speed directly impacts overall response time.

Storage Latency

Delay in reading or writing data from storage devices. SSDs provide sub-millisecond latency, while traditional HDDs require 5-10 ms. Cloud storage introduces additional network latency on top of storage device latency.

Compute Latency

Delay introduced by application or server processing. Complex AI models, inefficient algorithms, or resource contention increase compute latency. Model optimization techniques like quantization and pruning specifically target compute latency reduction.

In AI pipelines, these latency types compound multiplicatively. A 100 ms network delay plus 200 ms compute latency plus 50 ms retrieval latency results in 350 ms total user-perceived latency—often unacceptable for real-time applications.

Why Latency Matters

User Experience: Studies consistently show that response times exceeding 100 ms are perceptible to users, and delays beyond 1 second significantly impact engagement. E-commerce sites experience measurable conversion rate decreases with every 100 ms of additional latency.

Application Performance: Low latency is essential for responsive web and mobile applications, real-time analytics and decision-making, AI-powered search and retrieval, cloud computing and API integration, and interactive media experiences.

Business Impact: In high-frequency trading, 1 ms delay can result in significant financial loss or missed opportunities. In streaming services, high latency causes buffering and subscriber churn. In healthcare applications, delays can impede diagnosis or real-time interventions.

AI-Specific Concerns: For AI chatbots, high latency degrades conversational experience. For autonomous systems, even slight delays pose safety risks. For recommendation systems, slow responses lead to user abandonment before recommendations load.

Common Use Cases

Online Gaming

Multiplayer games require minimal latency (typically <50 ms) for real-time interaction. High latency causes lag, severely affecting gameplay, competitive fairness, and user satisfaction. Professional esports demand single-digit millisecond latencies.

Financial Services

Automated trading systems execute orders where microseconds matter. Colocation facilities placing servers physically next to exchanges minimize network latency. Algorithmic trading strategies specifically account for expected latency in their execution logic.

Web Applications

Users expect instant loading and seamless interactions. Slow API responses or database queries degrade application performance and user satisfaction. Content delivery networks (CDNs) specifically address latency by caching content geographically closer to users.

Healthcare Systems

Telemedicine, remote surgery, and clinical data retrieval require low latency for safety and effectiveness. Real-time patient monitoring systems must detect critical events within milliseconds to enable timely intervention.

AI/ML Pipelines

Real-time inference and semantic search depend on fast data retrieval. High retrieval latency creates bottlenecks in model throughput and degrades user experience. Vector database optimization specifically targets retrieval latency reduction.

Primary Causes

Physical Distance

Greater distance between endpoints increases latency proportionally. Light travels at finite speed (approximately 200,000 km/s in fiber), creating fundamental physical limits. Cross-continental requests inherently require 50-100 ms just for signal propagation.

Transmission Medium

Different media exhibit vastly different latency characteristics:

• Fiber optic: 1-10 ms (typical)
• Copper ethernet: <1 ms (local)
• 4G LTE: 20-50 ms
• 5G: <10 ms
• Satellite: 500+ ms (geosynchronous orbit)

Network Hops

Each router, switch, or firewall adds processing time. Typical enterprise networks involve 10-15 hops, each contributing 1-5 ms. Optimized routing can significantly reduce hop count.

Network Congestion

High traffic volume causes queuing delays as routers buffer packets. Congestion can increase latency by 10× or more during peak periods. Quality of Service (QoS) policies can prioritize latency-sensitive traffic.

Server Performance

Inefficient server processing increases latency. Factors include:

• CPU/memory resource contention
• Inefficient database queries
• Blocking I/O operations
• Unoptimized code paths

Storage Performance

HDDs: 5-10 ms average latency SSDs: <1 ms typical latency NVMe SSDs: <0.1 ms for reads Network storage adds network latency on top of device latency

Measurement Methods

Time to First Byte (TTFB)

Time from initiating request to receiving first byte of response. Indicates both server processing and network delay. Web performance tools measure TTFB as primary metric for server responsiveness.

Round-Trip Time (RTT)

Time for data packet to travel from source to destination and back. Core metric for network latency, measured using tools like ping. Minimum achievable application latency cannot be less than RTT/2.

Ping Command

Sends ICMP packet to destination, measures return time. Lower ping indicates lower latency and more responsive connection. However, ping measures only network layer latency, not application layer performance.

Application-Specific Metrics

Retrieval Latency: Time from query to data retrieval completion—vital in AI and search systems.

Inference Latency: Time from input to model output in AI systems.

P50/P95/P99 Latency: Percentile measurements capturing distribution. P95 latency means 95% of requests complete faster than this threshold.

Latency vs. Related Concepts

Bandwidth

Maximum data transmitted over network per second (Mbps, Gbps). Bandwidth is pipe width; latency is how quickly water starts flowing. High bandwidth does NOT guarantee low latency. 10 Gbps satellite link still has 500+ ms latency.

Throughput

Actual data successfully transferred per unit time. Affected by both bandwidth and latency. Low latency enables higher throughput in interactive protocols.

Jitter

Variation in latency over time. High jitter disrupts real-time applications like VoIP or video streaming. Jitter of ±50 ms makes video conferencing nearly unusable.

Packet Loss

Percentage of data packets not reaching destination. Packet loss often triggers retransmission, effectively increasing latency. 1% packet loss can double effective latency in TCP connections.

Reduction Strategies

Content Delivery Networks

Cache content geographically close to users, minimizing physical distance for data delivery. CDNs can reduce latency by 50-80% for static content through edge caching.

Edge Computing

Moves computation and data storage closer to end users, reducing round-trip time. Critical for IoT, autonomous vehicles, and real-time AI inference applications.

Network Infrastructure Upgrades

Upgrade routers, switches, and cabling to modern standards. Migrate to fiber optic links where feasible. Replace aging equipment that introduces unnecessary processing delays.

Server and Application Optimization

Refactor server code, optimize database queries, minimize blocking operations. Database query optimization alone can reduce latency by 10-100×. Asynchronous processing prevents blocking.

Caching Strategies

Store frequently accessed data in fast-access memory. Redis and Memcached provide sub-millisecond access to cached data. Effective caching can eliminate 80-90% of database queries.

Load Balancing

Distribute requests across multiple servers to prevent any single server from becoming bottleneck. Geographic load balancing routes users to nearest data center.

Protocol Optimization

Use optimized protocols for specific use cases:

• HTTP/2 and HTTP/3 reduce connection overhead
• QUIC provides faster connection establishment
• UDP for latency-sensitive real-time applications

Database Optimization

• Add appropriate indexes to tables
• Optimize query execution plans
• Use connection pooling
• Implement query result caching
• Consider read replicas for read-heavy workloads

Application-Level Optimizations

• Lazy loading for non-critical resources
• Code splitting to reduce initial bundle size
• Prefetching likely user actions
• Optimistic UI updates before server confirmation

Industry Solutions

AWS Services

AWS Direct Connect: Dedicated network connections reducing latency and variability.

Amazon CloudFront: Global CDN for low-latency content delivery with 400+ edge locations.

AWS Global Accelerator: Routes traffic through optimal AWS edge location using anycast.

AWS Local Zones: Deploys AWS services closer to population centers for ultra-low latency.

Cloud Providers

Google Cloud CDN: Edge caching with Google’s global network infrastructure.

Azure Front Door: Global load balancing and CDN with low-latency routing.

Cloudflare: Edge computing platform with extensive global presence.

Specialized Solutions

IBM Edge Computing: Deploys compute resources at edge for latency-sensitive workloads.

AI21 RAGCache: Reduces retrieval latency in AI pipelines through intelligent caching.

Frequently Asked Questions

What is considered “good” latency? Depends on use case. Interactive applications: <100 ms. Real-time gaming: <50 ms. High-frequency trading: <10 ms. Voice/video: <150 ms. Each application has specific requirements.

Does high bandwidth reduce latency? Not necessarily. Bandwidth affects how much data transfers, not how quickly individual packets travel. 10 Gbps satellite link still has 500+ ms latency due to physical distance.

Can latency be completely eliminated? No. Physical limits (speed of light) create minimum latency based on distance. Best achievable latency is physical distance divided by signal propagation speed.

How does retrieval latency affect AI systems? High retrieval latency slows inference and real-time decision-making, directly impacting effectiveness of AI-powered search, recommendations, and chatbots.

What causes variable latency? Network congestion, resource contention, thermal throttling, background processes, and routing changes all contribute to latency variation (jitter).

Best Practices

Measure Continuously: Implement comprehensive monitoring of latency metrics across all system components.

Set Clear Targets: Define acceptable latency thresholds based on user experience requirements and business needs.

Optimize Critical Paths: Focus optimization efforts on components contributing most to end-to-end latency.

Plan for Scale: Ensure latency remains acceptable as user base and data volumes grow.

Test Realistically: Measure latency under production-like loads and geographic distributions.

Monitor Percentiles: Track P95 and P99 latency, not just averages, to catch outliers affecting users.

References

• AWS: What Is Latency?
• IBM: What Is Latency?
• MDN: Understanding Latency
• Fortinet: What Is Latency
• Galileo AI: Understanding Latency in AI
• AI21: Retrieval Latency
• WEKA: Solving Latency Challenges
• DriveNets: Latency in AI Networking
• AWS CloudFront
• AWS Direct Connect
• AWS Global Accelerator
• AWS Local Zones
• Investopedia: High-Frequency Trading
• MDN: Time to First Byte
• AWS: What is Throughput?