diff --git a/src/pg.ml b/src/pg.ml
new file mode 100644
index 00000000..8b3e39f8
--- /dev/null
+++ b/src/pg.ml
@@ -0,0 +1,53 @@
+(* TODO be sure to not use postgres ptime
+   add a dune stanza like for prelude:
+   "(flags (:standard -open Prelude))" *)
+module Caqti_type = struct
+  include Caqti_type
+
+  let ptime_to_int64 ptime =
+    ptime |> Ptime.to_float_s |> Int64.of_float |> Result.ok
+
+  let ptime_of_int64 i =
+    match Ptime.of_float_s (Int64.to_float i) with
+    | None -> Fmt.error "ptime_of_int64 error: `%Ld` is not a valid ptime" i
+    | Some ts -> Ok ts
+
+  (* we want to use int64 timestamps,
+     not postgresql built-in timestamp type *)
+  let ptime : Ptime.t Caqti_type.t =
+    Caqti_type.custom ~encode:ptime_to_int64 ~decode:ptime_of_int64
+      Caqti_type.(int64)
+end
+
+let pg_amount : Amount.t Caqti_type.t =
+  let open Amount in
+  (* TODO bad int32 conversion *)
+  Caqti_type.custom
+    ~encode:(fun amount -> Ok (amount.value, Int64.to_int32 amount.fraction))
+    ~decode:(fun (value, fraction) ->
+      let fraction = Int64.of_int32 fraction in
+      Ok { sign= None; currency= `Eur; value; fraction })
+    Caqti_type.(t2 int64 int32)
+
+(* WIP: minimum db functions for basic /management *)
+
+let pg_todo () = assert false
+
+(* signkey *)
+let activate_signing_key = pg_todo
+let lookup_signing_key = pg_todo
+let iterate_active_signkeys = pg_todo
+let insert_signkey_revocation = pg_todo
+let lookup_signkey_revocation = pg_todo
+
+(* denominations *)
+let insert_denomination_info = pg_todo
+let get_denomination_info = pg_todo
+let get_denomination_by_serial = pg_todo
+let iterate_denomination_info = pg_todo
+let iterate_denominations = pg_todo
+let get_coin_denomination = pg_todo
+let insert_denomination_revocation = pg_todo
+let get_denomination_revocation = pg_todo
+let lookup_denomination_key = pg_todo
+let add_denomination_key = pg_todo