Anatomy of a Low-Latency Origin Service
We’ve all been there: you fire up a live stream of a big game or breaking news event, only to stare at a spinning wheel while your friends across town are already cheering at the action. A few seconds of delay or buffering might not seem like much, but in live streaming, it can mean the difference between being part of the moment or playing catch-up.
At the core of every streaming workflow is the origin server—the system that receives encoded video segments and playlist files from an encoder and makes them available to the distribution network. The origin acts as the authoritative source for the stream, ensuring that each request from a video player, whether for the latest HLS segment or an updated manifest, is served with accuracy and speed. Its performance directly impacts startup latency, playback stability, and the ability of a stream to scale to millions of concurrent viewers.
Streaming workflow schematic with the origin server at the core
In HLS (HTTP Live Streaming), live events typically have a unique manifest path, providing players with a consistent URL and simplifying the logic required to access the stream. The encoder periodically generates and uploads new manifests, overwriting the previous one with updated segment listings as the stream progresses. Video players continuously fetch the manifest, parse the latest segment references, and request those segments for playback—creating the seamless experience of watching live content in near real time.
The challenge is that traditional object storage systems are not designed for this access pattern. Each time the manifest is updated, it must be made available to players instantaneously—a property known as strong read-after-update consistency—so viewers always see the latest segments. Without it, players risk fetching stale manifests, leading to noticeable playback delays or even missing live moments. Reads from the origin must also complete with extremely low latency, since every request for a manifest or segment directly affects startup time and playback smoothness; if these reads are slow, the viewer experiences buffering or lag behind the live edge. Finally, the system must guarantee high durability to ensure that once a segment is written, it is reliably stored and retrievable. A lack of durability can result in dropped segments or playback errors, breaking the continuity of the stream and undermining viewer trust.
These challenges can be addressed by an Origin service that leverages a multi-tiered storage approach, designed around the unique access patterns of live video. Unlike traditional object storage, which is designed for large files, live streaming content is composed of small segments (e.g., around 15 MB for a 20 Mbps 4K stream) that can be managed more efficiently when the system is tuned for small object sizes. Furthermore, each segment is only relevant for a brief window of time, as players quickly advance to newer segments in the stream. In practice, this means that more than 95% of all read requests concentrate on a small, active set of segments, allowing the origin to prioritize performance and consistency where it matters most.
A multi-tiered storage approach
The Origin service can be structured around several key components that work together to handle the demands of live streaming. At the front is the interface layer, which connects both to the live encoder publishing new manifests and segments, and to the players retrieving them for playback. Behind this lies an object metadata service that maintains the location and versioning information for every object within the system. The storage itself is divided into two tiers: Tier 1 is a low-latency, high-performance layer, often built on in-memory systems such as Memcached or Redis, while Tier 2 is a disk-based layer optimized for lower-cost archival. Objects are first ingested into Tier 1, and after a short period—once the stream has advanced—are moved into Tier 2 for longer-term retention.
Durability
Durability is ensured by replicating ingested data into multiple copies across the Origin service. These replicas are typically distributed across different availability zones, maximizing fault tolerance and resilience against hardware or network failures. By maintaining several independent copies, the system guarantees that even if a storage node or an entire zone becomes unavailable, the data remains accessible.
For viewers, this means uninterrupted playback and a reduced risk of errors caused by missing or corrupted segments.
Strong Consistency
Strong consistency is maintained by creating new versions of objects instead of overwriting existing ones. Each version is tracked and managed within the object metadata, which ensures that players always receive the latest valid manifest or segment. This design eliminates the risk of players reading stale data—such as an outdated manifest that does not reference the newest segments—which could otherwise result in playback delays or users falling behind the live edge.
Performance
Performance at the live edge is driven by the use of in-memory storage for newly written objects. Keeping these segments in Tier 1 storage minimizes read latency and allows players to retrieve content quickly, enabling smooth, buffer-free playback. The replication of objects across multiple hosts further enhances performance by distributing read requests, preventing hotspots, and ensuring that large numbers of concurrent viewers can be served without bottlenecks.
Cost
Cost efficiency is achieved by aligning storage tiers with the natural lifecycle of live streaming content. Segments that are no longer at the live edge are automatically moved to Tier 2 disk-based storage, which provides lower-cost archival without sacrificing availability. Additionally, because live events are often scheduled and predictable, Tier 1 resources can be scaled up to handle peak workloads during broadcasts and scaled down afterward. This elasticity helps minimize the expense of maintaining high-performance storage without compromising the viewing experience.
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