Knowledge section
Concepts
Atomic engineering ideas that recur across distributed systems, backend platforms, and reliability work.
intermediate
Adaptive Bitrate Streaming
Serve video as small segments at multiple quality levels so players can switch bitrate while playback continues under changing network conditions.
foundation
Analytics Pipelines
Systems that collect high-volume product events and transform them into metrics, dashboards, aggregates, and behavioral signals.
intermediate
Backpressure
A system's ability to respond safely when downstream components cannot keep up with incoming work.
foundation
Caching
Store frequently needed data closer to the request path so systems can reduce latency, absorb read pressure, and protect slower backing stores.
intermediate
CDN Edge Caching
Cache static or semi-static assets near users so high-volume reads avoid distant origins and media playback can survive global traffic pressure.
intermediate
Conflict Resolution
Decide what happens when multiple devices or services change related state concurrently and no single update can safely overwrite the others.
foundation
Database Indexing
Organize database data structures so common reads can find the right rows quickly without scanning the entire table.
intermediate
Delivery Guarantees
The reliability contract that defines whether messages can be lost, duplicated, retried, acknowledged, or eventually delivered.
intermediate
Delta Transfer
Move only the changed portions of data between client and server so sync can recover quickly without re-sending entire files.
foundation
Derived Projections
Read-optimized views computed from source-of-truth data or events so systems can answer common product queries quickly.
advanced
Dispatch Matching
Select and reserve the best available supply for a demand request under changing location, availability, ETA, fairness, and concurrency constraints.
intermediate
Distributed Counters
Counter designs that avoid a single hot bottleneck when many machines update or read the same logical count.
intermediate
Event Streams
Durable ordered logs of events that let systems publish state changes and let independent consumers process them asynchronously.
foundation
Eventual Consistency
A consistency model where replicas, caches, or projections may temporarily disagree but are expected to converge if processing continues.
intermediate
Fan-Out
The process of taking one event or request and distributing work to multiple downstream consumers, services, users, or projections.
intermediate
File Chunking
Split large files into smaller addressable pieces so upload, download, deduplication, retry, and sync can work without moving the whole file every time.
intermediate
Geospatial Indexing
Partition physical space into searchable cells so nearby entities can be found without scanning every location record.
advanced
Group Message Fan-Out
The scaling problem created when one group message expands into many recipient, device, receipt, push, and projection updates.
intermediate
Hot Key Mitigation
Techniques for handling keys or records that receive disproportionate traffic and threaten to overload a partition, cache node, or database row.
foundation
HTTP Redirects
How servers tell clients to navigate to another URL, and why redirect status codes affect caching, mutability, analytics, and control.
foundation
Idempotency
A reliability property that lets clients safely retry uncertain operations without creating duplicate business side effects.
intermediate
Idempotent Consumers
Event consumers that can safely process the same message more than once without duplicating side effects.
intermediate
Inverted Index
Map searchable terms to the documents that contain them so search can find candidates without scanning every document.
intermediate
Live Playback Window
Maintain the moving set of playable live segments that lets players stay near the live edge without depending on media that has not been produced yet.
intermediate
Live Video Ingest
Receive, validate, and protect a real-time video feed so a live streaming platform can encode and publish the event while it is happening.
intermediate
Location Streams
Continuous movement updates from mobile clients that let realtime systems track approximate entity position without treating every coordinate as permanent truth.
intermediate
Media Message Pipeline
The upload, processing, storage, reference, and delivery flow that keeps large media files out of the core message path.
intermediate
Message Ordering
The rules and mechanisms that make messages appear in a coherent conversation order despite retries, concurrency, and distributed delivery.
intermediate
Message Receipts
Acknowledgement events that turn raw delivery activity into user-visible sent, delivered, read, and unread states.
intermediate
Metadata Sync
Keep file names, folders, permissions, versions, tombstones, and device cursors coherent while file bytes move through a separate storage path.
advanced
Multi-CDN Routing
Route playback traffic across multiple CDN providers or delivery paths so a live event can survive regional failures, overload, and uneven network performance.
intermediate
Multi-Device Sync
The model that lets one account use several devices while keeping messages, cursors, receipts, and local state coherent.
intermediate
Offline Delivery
The mechanisms that let disconnected users receive accepted messages later through durable logs, cursors, queues, and sync.
intermediate
Playback Manifests
Describe the available video renditions, segments, tracks, and URLs so players can stream media without guessing where playback assets live.
intermediate
Presence
A time-bounded signal that estimates whether a user or device is reachable, recently active, idle, or unavailable.
intermediate
Projection Drift
When a derived read model or aggregate becomes inconsistent with the source-of-truth data it was computed from.
intermediate
Push Notification Handoff
The process of waking or notifying offline devices after durable message acceptance without making push providers the source of truth.
intermediate
Query Fan-Out
Send one user query to many shards or services, merge the partial results, and return a ranked response within a latency budget.
intermediate
Ranking Signals
Use measurable document, query, freshness, and engagement signals to order search results by usefulness instead of returning raw matches.
foundation
Rate Limiting
Control how frequently clients can perform actions so systems remain available, fair, and protected from accidental or abusive overload.
foundation
Read Replicas
Copies of a primary database that serve read traffic so systems can scale reads and reduce pressure on the write database.
intermediate
Realtime Gateways
Connection-facing services that keep clients reachable in real time while leaving durable message truth to backend systems.
intermediate
Search Indexing Pipeline
Move newly created or updated documents from the write path into searchable indexes with bounded freshness and retryable processing.
intermediate
Sharding
Split data across multiple partitions or databases so a system can scale beyond one machine or one storage node.
foundation
Short-Code Generation
How systems create compact, unique identifiers for resources such as shortened URLs while balancing length, collision risk, predictability, and coordination.
intermediate
Version History
Preserve older states of a file or object so users and systems can recover from overwrites, conflicts, deletes, corruption, and delayed sync.
intermediate
Video Transcoding
Convert an uploaded video into playback-ready encodings, resolutions, bitrates, and segments so many devices and networks can stream it reliably.