Design Video Streaming Platform

On-demand and live video streaming platform with ingest, transcoding, DRM licensing, CDN delivery, ABR manifests, and playback analytics.

Functional requirements

  • Upload VOD content via web/API with resumable transfers.
  • Transcode uploads into multiple renditions (bitrate/resolution/codecs) and package into HLS/DASH.
  • Serve manifests and segments globally via CDN with tokenized/signed access.
  • Support DRM (e.g., Widevine/FairPlay/PlayReady) with license issuance and key rotation.
  • Provide live streaming ingest (RTMP/SRT) with near real-time segmenting and ABR manifests.
  • Store and deliver subtitles/captions and thumbnails/preview sprites.
  • Playback analytics collection — startup time, rebuffer ratio, bitrate switches, errors.
  • Search/browse catalog by title, genre, and availability; personalized recommendations.
  • Geo-blocking, entitlement checks, and availability windows per asset.
  • Multi-device playback support across web, mobile, and TV apps.

Non-functional requirements

  • Availability: 99.99% platform uptime; live events must remain available during a single-AZ failure.
  • Performance: initial playback start < 2 s p95; segment delivery < 150 ms p95 from edge; license issuance < 200 ms p95.
  • Scalability: support millions of concurrent viewers and petabyte-scale libraries.
  • Durability: source media and renditions stored with 11-nines durability in multi-AZ object storage.
  • Consistency: strong for entitlements and license issuance; eventual (< 30 s) for analytics and catalog search indexing.
  • Security: TLS in transit; signed URLs/cookies for CDN; DRM keys protected by KMS; principle of least privilege.
  • Resilience: circuit breakers/timeouts; retries with backoff; DLQs for failed jobs; blue/green or canary deployments.
  • Observability: traces/logs/metrics for ingest, packaging, origin, CDN hit ratio, and license latency.
  • Cost: storage tiering for cold content; CDN offload targets > 90% hit ratio.

How the design evolves

Stage 1: Monolith MVP

Single service handles upload, simple transcode trigger, and serving via origin; metadata in one DB.

What was missing: Edge/CDN, caching, async processing, and service isolation.

Why that's risky: SPOF and poor QoE under load.

What gets added: Nothing yet (MVP).

Trade-offs: Fast to build but not production ready.

Stage 2: Edge, CDN, and Rate Limiting

Add CDN for global delivery, edge ingress, and throttling before origin.

What was missing: Global delivery and ingress protection.

Why that's risky: Origin overload and poor latency.

What gets added: CDN, edge, and rate limiting.

Trade-offs: Cache invalidation and signed URL management.

Stage 3: Horizontal Scale and Manifest Cache

Scale origin/API and cache hot manifests/entitlements.

What was missing: Horizontal scale and hot-path caching.

Why that's risky: Origin bottlenecks and slow startup.

What gets added: Origin LB, replicas, and manifest cache.

Trade-offs: Cache invalidation and consistency management.

Stage 4: Split Services and Async Encoding Pipeline

Introduce domain services and queue-driven transcoding/packaging.

What was missing: Domain isolation and background processing for heavy work.

Why that's risky: Origin/CPU saturation on synchronous paths.

What gets added: Ingest, manifest, origin services; queue + transcoder/thumbnail workers.

Trade-offs: More services and operational complexity.

Stage 5: DRM Licensing and Live Ingest

Add DRM license service and live streaming ingest/segmenter while preserving VOD pipeline.

What was missing: DRM licensing and live ingest path.

Why that's risky: Content leakage and poor live QoE without dedicated flows.

What gets added: License service, live segmenter, and reinforced pipeline with queues.

Trade-offs: DRM key management and extra operational overhead.

Stage 6: Multi-Region Origin and Observability

Add regional origins and monitoring while preserving the full pipeline.

What was missing: Regional origins and robust observability.

Why that's risky: Single-region failures and poor incident visibility.

What gets added: Regional origins, DB replica, and monitoring/tracing.

Trade-offs: Cross-region consistency and operational complexity.

Frequently asked questions

How do you minimize playback startup time?

Use a CDN with pre-warmed caches for hot content, cache manifests/entitlements, and prioritize delivering the first few segments from the closest edge. Keep manifests small and enable HTTP/2 or HTTP/3 for parallel fetches.

How do you design the transcoding pipeline for scale?

Produce jobs per rendition and codec to a queue; workers autoscale with queue depth. Ensure idempotent outputs using deterministic keys. Use spot/low-cost instances as workers with checkpointing for long encodes, and store artifacts in object storage.

How do you secure content while keeping playback snappy?

Use DRM with short-lived licenses, signed URLs/cookies on the CDN, and entitlement checks cached for seconds. Keys stay in a KMS; services use least-privilege to request decryption operations.

How do you collect and process playback analytics at scale?

Send client-side playback events to an ingestion endpoint that writes to a durable queue. Batch-process with workers to aggregate QoE metrics and store rollups for dashboards and alerting.

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