Publish/Subscribe
Broadcast to every subscriber, as distinct from work distribution.
6 to work through
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intermediate
A team must choose between publish-subscribe and a work queue for a new integration. What distinguishes them, and which failure mode does each have?
2 min answer -
advanced
A chat platform uses publish/subscribe to deliver messages to connected clients. What breaks when a channel has a million members, and what changes?
2 min answer -
advanced Multiple choice
A payments service publishes PaymentCaptured to a topic with four subscribers. A fifth team needs the same event plus the payer's full name and address, which the producer does not emit because those fields are restricted. The fifth team proposes subscribing and then calling the producer per event to fetch them - about 900 extra reads a second. Which design fits?
3 min answer -
advanced Multiple choice
A social feed becomes too expensive to generate at read time. Should the system fan out on write, fan out on read, or use a hybrid - and what decides it?
2 min answer -
advanced
An interviewer says - design the delivery path for a live cricket scorecard to a peak concurrent audience of the size Hotstar reported for the 2023 World Cup final, around 59 million. Walk me through the clarifying questions that change the design, then your first architecture.
3 min answer -
advanced
In a team chat product, a message posted to a channel with 8,000 members must reach everyone connected. Design the delivery path.
2 min answer
4 terms in this topic
Fan-Out Delivery
Delivering one published message to many independent subscribers, each with its own copy, position and failure handling.
practiceFan-out Threshold
The membership or follower count at which a system switches from pushing to recipients to having recipients pull - and the monitoring that keeps the …
patternPublish-Subscribe
One publication delivered to many subscribers, with the publisher unaware of who they are — and the fan-out problem that comes with it.
conceptSemantic Coupling
Dependence on what an event or field means rather than on its shape - the coupling that survives every schema check, breaks nothing when violated, an…
Neighbouring topics
Architecture Patterns
General material on architectural patterns and their trade-offs.
Layered Architecture
The default shape, its clarity, and where a technical partition fails.
Event-Driven Architecture
Publishing facts, and trading comprehensibility for decoupling.
Pipes and Filters
Independent transformation steps composed into a pipeline.
Competing Consumers
Scaling throughput with instances, at the cost of ordering.
Saga
Local transactions with compensating actions across services.
CQRS
Separate models for writing and reading, each optimised for its job.
Event Sourcing
The event log as the system of record, with state as a projection.
Outbox
Making the event atomic with the business write it describes.
Strangler Fig
Incremental replacement behind a routing facade.
Anti-Corruption Layer
Translating a foreign model at the boundary so it does not leak in.
Sidecar & Ambassador
Cross-cutting behaviour in a co-deployed process.
Service Mesh
Sidecars applied estate-wide, and the scale at which that pays.
API Gateway
A single entry point for policy, routing and protocol translation.
Backend for Frontend
A narrow backend per client experience, owned by that client's team.
Cell-Based Architecture
Complete isolated copies each serving a subset of customers.
Sharding Patterns
Directory versus embedded keys, logical shards and rebalancing.
Materialized Views
Precomputed query results, refreshed incrementally or in full.
Orchestration vs Choreography
A coordinator that knows the flow, or services that react to events.