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edge_architecture.md (4206B)

      1 # Edge Architecture
      2 
      3 Edge Architecture utilizes a tiered architecture to move data as close to the
      4 end user as possible while protecting the origin from traffic spikes.
      5 
      6 ```
      7                     +-------------------+
      8                     |    Developer      |
      9                     | (npm/docker pull) |
     10                     +---------+---------+
     11                               |
     12                               v
     13                     +-------------------+
     14                     | Anycast / Geo-DNS |
     15                     +---------+---------+
     16                               | (Routes to nearest PoP)
     17                               v
     18 +-----------------------------------------------------------+
     19 |                       EDGE PoP                            |
     20 |                                                           |
     21 |  +-------------+    +---------------+   +--------------+  |
     22 |  | Edge Compute|--->| L1 Cache      |   | WAF / DDoS   |  |
     23 |  | (Auth/Route)|    | (Memory/NVMe) |   | Protection   |  |
     24 |  +-------------+    +-------+-------+   +--------------+  |
     25 +-----------------------------|-----------------------------+
     26                               | (Cache Miss)
     27                               v
     28 +-----------------------------------------------------------+
     29 |                  REGIONAL SHIELD CACHE                    |
     30 |  +-----------------------------------------------------+  |
     31 |  |   L2 Cache (High Capacity SSD, Request Collapsing)  |  |
     32 |  +--------------------------+--------------------------+  |
     33 +-----------------------------|-----------------------------+
     34                               | (Cache Miss)
     35                               v
     36 +-----------------------------------------------------------+
     37 |                   ORIGIN INFRASTRUCTURE                   |
     38 |  +--------------------+       +------------------------+  |
     39 |  | Blob Storage       |       | Global Metadata DB     |  |
     40 |  | (S3 / GCS)         |       | (Spanner / DynamoDB)   |  |
     41 |  +--------------------+       +------------------------+  |
     42 +-----------------------------------------------------------+
     43 ```
     44 
     45 To achieve this scale, the technology stack must be highly concurrent and
     46 lightweight:
     47 
     48 - **Edge Routing & Proxy**: NGINX, Envoy, or Rust-based proxies to handle
     49   millions of concurrent TCP connections and perform TLS termination.
     50 
     51 -- **Edge Compute**: WebAssembly (Wasm) or V8 Isolates running directly on the
     52 CDN edge to execute custom logic like authentication, A/B testing, and request
     53 filtering without routing back to the origin.
     54 
     55 -- **Caching Layer**: Varnish or custom memory-mapped file systems for L1 edge
     56 caching, backed by high-capacity NVMe drives for L2 regional shields.
     57 
     58 -- **Data & Origin**: Geographically replicated object storage (like AWS S3) for
     59 immutable package blobs, and a globally distributed database (like Google Cloud
     60 Spanner) for mutable package metadata and user entitlements.
     61 
     62 ## System Data Flows
     63 
     64 When a user pulls a package, the request follows a strict path to ensure
     65 authorization and speed:
     66 
     67 -- **Resolution**: The client's DNS query hits a Geo-DNS provider, returning the
     68 Anycast IP of the nearest Edge PoP (Point of Presence).
     69 
     70 -- **Edge Auth**: The request reaches the Edge Proxy. An Edge Function executes
     71 immediately, verifying the user's API token against a highly cached subset of
     72 the metadata database.
     73 
     74 -- **Cache Lookup**: The proxy checks the L1 Cache. If the package is found, it
     75 is returned instantly.
     76 
     77 -- **Shield Fallback**: On an L1 miss, the request goes to the Regional Shield.
     78 If the package is present in the L2 cache, it is returned and populated in L1.
     79 
     80 -- **Origin Fetch**: On an L2 miss, the shield fetches the blob from Origin
     81 Storage, caches it, and streams it back down the chain to the client.
     82 
     83 ## Performance Impact Chart
     84 
     85 This tiered networking approach reduces latency across the distribution
     86 lifecycle.
     87 
     88 ```
     89           Average Response Latency (ms) by Retrieval Tier
     90 ------------------------------------------------------------
     91 Origin Fetch       |################################ (250ms)
     92 Regional Shield L2 |########### (85ms)
     93 Edge PoP L1        |### (20ms)
     94 Predictive Cache   |# (5ms)
     95 ------------------------------------------------------------
     96 `
     97 ```