If you work in the world of digital television or OTT streaming, you know the cold sweat that runs down your back when there’s a massive premiere or a football final. The fear isn’t so much that the CDN won’t respond, but that your origin server will decide to “shut down” due to the avalanche of requests.
If that’s your situation, I’ll tell you why you need a mid-tier layer. This layer, in addition to acting as a second-level (L2) cache, functions as an intelligence filter, a shield, and, if that weren’t enough, also as a cost-saving manager. All in one.
Imagine 10,000 users simultaneously requesting the same video clip. Without a mid-tier, your origin receives 10,000 cries for the same thing. However, with a mid-tier, the magic of request coalescing happens.
The mid-tier server receives the requests, realizes they’re all looking for the same .ts file, and tells the rest: “Wait a minute, I’ll get it.” It makes a single request to the origin, saves the file in its L2 cache, and distributes it to everyone simultaneously. Your origin server doesn’t even realize there’s an entire stadium watching the screen.
An older Smart TV, an iPhone, a game console, or any other device, has its own quirks. Some send unusual headers, others insert telemetry parameters into the URL, like ?user_id=123&session=abc. For a standard cache, each of these variations represents a separate file. This results in chaos and cache failures.
Using the same technology it uses to resolve these types of situations in CDN nodes, the Transparent Edge mid-tier applies header and query string normalization by doing the following:
video.mp4?a=1&b=2 and video.mp4?b=2&a=1 are recognized as what they are: the same blessed file.At edge nodes, space is expensive and content disappears quickly. If a video isn’t trending in the last five minutes, it’s evicted to make room for new content.
The dedicated mid-tier, however, has massive storage capacity. It acts as intermediate video storage where long-tail content resides. Because it doesn’t suffer constant evictions, it prevents edge nodes from having to search for that old episode of a series all the way back to the origin. The mid-tier always has it readily available.
If you manage a video platform, you know that the edge is like the front row of a festival: noisy, with people asking for different things, and generally chaotic. Traditionally, you want to trust the edge to handle everything, but when we’re talking about digital television at scale, you need a conductor.
That’s the function of the dedicated mid-tier. Besides offering you a larger cache, it’s where the magic of normalization and efficiency happens.
In the edge, the Vary header is both a blessing and a curse. If not handled properly, it can fragment your cache into a thousand pieces. The Transparent Edge mid-tier acts as a universal translator for the most common scenarios:
Accept-Encoding requests. If the origin only needs to send one version, the mid-tier ensures efficient caching, preventing the origin from doing double the work.Origin and Access-Control-Allow-Origin headers can be chaotic if you have multiple domains. The mid-tier standard normalizes these headers so that the cache key isn’t broken by a simple domain change, serving the correct content without having to return to the origin to ask, “Do I grant permission to this?“Accept-Language, the mid-tier system groups the requests. We don’t need 50 variants for 50 nuances of Spanish; the mid-tier system standardizes the request so the origin can rest easy.In summary: the mid-tier cleans up the “noise” coming from the edge and is the one who decides what information is really important to go and find at the origin.
This is where the mid-tier goes from being interesting to being essential. Many broadcasters use several CDNs (CDN1 for some countries, CDN2 for others, CDN3 for live broadcasts…).
The problem without a mid-tier system: every time a CDN fails a cache lookup, it goes straight to your origin. If you have three CDNs, your origin receives triple the load! It’s like three different delivery services, with all their minions, knocking on your door to order the same pizza.
The solution with a dedicated mid-tier involves making the mid-tier the single entry point for all your CDNs. This way you achieve:
In television, making a mistake is not an option. That’s why we’ve designed a Murphy’s Law-proof redundancy system:
Let’s talk about money. In the cloud, egress (outgoing traffic) is the tax that hurts the most.
| CONCEPT | WITHOUT MID-TIER (standard L1 cache) | WITH DEDICATED MID-TIER |
|---|---|---|
| Traffic served to users | 1 Petabyte | 1 Petabyte |
| Traffic delivered from the origin to the edge nodes | ~15% (150 TB) | ~1-2% (10 TB) |
| Egress cloud invoice | $$$ (high) | $ (minimum) |
| Load on servers/packagers | High (dangerous peaks) | Flat and predictable |
In a scenario of 1PB per month, the savings in egress costs can exceed €84,000 per year.
In a DDoS cyberattack scenario, the mid-tier is your first line of defense. Your origin server is no longer exposed to the internet and becomes isolated. It only communicates with the mid-tier server. And if someone tries to take down the service with a Layer 7 flood attack, the mid-tier server absorbs the impact. It’s much harder to overwhelm Transparent Edge’s dedicated infrastructure than a conventional origin server.
Implementing a mid-tier is a sound technical decision because you protect your origin, make your operations team happy, and, incidentally, save the company a fortune in infrastructure costs.
Furthermore, in a world where traffic is volatile and devices are infinite, the mid-tier is the piece that brings sanity, as it manages Vary like an expert, unifies your CDNs, and allows you to sleep soundly knowing that, even if you have a record-breaking audience success, your origin server will be as relaxed as if it were a Sunday morning.
Let’s talk about how to secure your platform and start saving on your next cloud bill?
Oscar Dorrego is Presales at Transparent Edge.
Psychologist by training, computer scientist by hobby, pre-sales by profession, new romantic at heart. He does so many things that he doesn’t even remember what he really does. More left hand than Nadal. Living between business and technology allows him to have half the joys and twice the worries, but it is impossible to make a dent in the spirit of our favorite snake charmer.
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