What is the difference between push and pull architectures?
Why Interviewers Ask This
Foundational questions like this help interviewers calibrate the rest of the interview. A confident, accurate answer signals that you have solid System Design basics — a prerequisite for any developer role.
Answer
Push architecture: the server/producer actively sends data to clients/consumers when new data is available. The server initiates the communication. Examples: WebSockets, server-sent events (SSE), webhooks, Kafka push to consumers. Pros: low latency (data delivered immediately when available), no polling overhead, real-time. Cons: server must maintain connections, can overwhelm slow consumers (need back-pressure), requires persistent connection (WebSockets) or pre-registered endpoint (webhooks). Pull architecture: the client/consumer periodically requests data from the server/producer. The consumer initiates the communication. Examples: REST API polling, Kafka consumer pulling from topic, database queries. Pros: consumer controls its processing rate (natural back-pressure), simpler server (stateless), works across firewalls/NAT. Cons: inherent latency (must wait for next poll), wasted requests when no new data (polling overhead). Long polling: hybrid — client sends a request, server holds it open until new data is available, then responds. Lower latency than short polling. When to use each: push when real-time delivery matters and connections are manageable (chat, notifications, live feeds); pull when consumers have varying processing speeds and connection management is complex (batch processing, ETL, Kafka consumers). Most systems use both patterns in different parts of the architecture.
Pro Tip
If you're unsure about a detail, say so honestly and explain your reasoning. Interviewers respect candidates who can think through uncertainty rather than bluffing.