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Realtime Applications

Design ordered, authorized, observable realtime sessions.

Advanced
9 lessons
2 projects
About 1.5h
EN · UZ · KO

Model connection lifecycles, WebSocket messages, reconnect backoff, ordering, deduplication, presence expiry, authorization, backpressure, and observability without assuming a perfect network.

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Curriculum

Section 1
Connection Lifecycle
Open, authenticate, close, and reconnect deliberately — handshake, states, and backoff before anything else.
1. WebSocket Handshake
2. Connection State Machines
3. Reconnect with Backoff
Section 2
Message Correctness
Handle duplicates, gaps, and pressure explicitly — sequence numbers, idempotent events, and bounded queues.
1. Sequence Numbers
2. Idempotent Events
3. Backpressure
Section 3
Presence, Authorization & Operations
Treat presence as expiring evidence, check every subscription, and observe the whole session.

Learning paths

Full-Stack Web Developer

Build and share a tested full-stack React app: a screen everyone can use, data only its owner can see, APIs with clear limits, realtime updates that stay correct, and deploys you can roll back.

14 course sequence

Try one lesson. Then build the habit.

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Curriculum

Connection Lifecycle

Message Correctness

Presence, Authorization & Operations

Learning paths

Full-Stack Web Developer

Try one lesson. Then build the habit.