diff --git a/ARCHITECTURE.md b/ARCHITECTURE.md
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@@ -1,3 +1,81 @@
 # Architecture
 
-...
+[Luigi](https://github.com/spotify/luigi) for orchestration (but trying to keep
+task code minimal). Structured directories and filenames for data artifacts.
+
+![](static/labe-tree.png)
+
+The result are three [sqlite3](https://sqlite.org/) databases:
+
+* a) id-doi "mapping" database
+* b) "citations" databases (doi-doi)
+* c) index "metadata" key value store (id-doc)
+
+There is one "mapping" and one "citations" database, but there can be one or
+more "metadata" databases.
+
+A server assembles fused results from these databases on the fly (and caches
+expesive requests).
+
+![](static/Labe-Sequence.png)
+
+This way we should get a good balance:
+
+* we need *little preprocessing*, we mostly turn CSV or SOLR JSON into sqlite databases
+* we still can *be fast* through caching, which can be done forehandedly ("cache
+  warming") or as data is actually requests
+
+The server delivers JSON responses, which can be included in catalog frontends.
+
+```json
+$ curl -sL "http://localhost:8000/doi/10.1016/s0273-1177(97)00070-7" | jq .
+{
+  "id": "ai-49-aHR0cDovL2R4LmRvaS5vcmcvMTAuMTAxNi9zMDI3My0xMTc3KDk3KTAwMDcwLTc",
+  "doi": "10.1016/s0273-1177(97)00070-7",
+  "cited": [
+    {
+      "author": [
+        "Meljac, Claire",
+        "Voyazopoulos, Robert"
+      ],
+      "doi_str_mv": [
+        "10.4000/rechercheseducations.819"
+      ],
+      "format": [
+        "ElectronicArticle"
+      ],
+      "id": "ai-49-aHR0cDovL2R4LmRvaS5vcmcvMTAuNDAwMC9yZWNoZXJjaGVzZWR1Y2F0aW9ucy44MTk",
+      "institution": [
+        "DE-Zi4",
+        "DE-14",
+        "DE-Ch1",
+        "DE-Gla1",
+        "DE-D161",
+        "DE-Brt1",
+        "DE-Pl11",
+        "DE-Rs1",
+        "DE-82",
+        "DE-D275",
+        "DE-15",
+        "DE-105",
+        "DE-L229",
+        "DE-Bn3",
+        "DE-Zwi2"
+      ],
+      "title": "Binet, citoyen indigne ?",
+      "url": [
+        "http://dx.doi.org/10.4000/rechercheseducations.819"
+      ]
+    }
+  ],
+  "unmatched": {},
+  "extra": {
+    "took": 0.001490343,
+    "unmatched_citing_count": 0,
+    "unmatched_cited_count": 0,
+    "citing_count": 0,
+    "cited_count": 1,
+    "cached": false
+  }
+}
+```