diff --git a/benchpress-server.opam b/benchpress-server.opam
index 03c237d..563f166 100644
--- a/benchpress-server.opam
+++ b/benchpress-server.opam
@@ -20,7 +20,7 @@ depends: [
   "gnuplot" { >= "0.6" & < "0.8" }
   "sqlite3"
   "sqlite3_utils" { >= "0.4" & < "0.5" }
-  "tiny_httpd" { >= "0.12" & < "1.0" }
+  "tiny_httpd" { >= "0.16" & < "1.0" }
   "printbox" { >= "0.6" }
   "printbox-text" { >= "0.6" }
   "ocaml" {>= "4.12" }
diff --git a/benchpress.opam b/benchpress.opam
index 5df3525..f3b3f6b 100644
--- a/benchpress.opam
+++ b/benchpress.opam
@@ -24,7 +24,7 @@ depends: [
   "processor"
   "pp_loc" { >= "2.0" & < "3.0" }
   "gnuplot" { >= "0.6" & < "0.8" }
-  "sqlite3"
+  "sqlite3" { >= "5.0.3" } # https://github.com/sneeuwballen/benchpress/pull/73#issuecomment-1764108025
   "sqlite3_utils" { >= "0.4" & < "0.6" }
   "printbox" { >= "0.6" }
   "printbox-text" { >= "0.6" }
diff --git a/src/bin/benchpress_bin.ml b/src/bin/benchpress_bin.ml
index 1f55696..f4f3102 100644
--- a/src/bin/benchpress_bin.ml
+++ b/src/bin/benchpress_bin.ml
@@ -19,9 +19,10 @@ module Run = struct
   (* sub-command for running tests *)
   let cmd =
     let open Cmdliner in
-    let aux j cpus pp_results dyn paths dir_files proof_dir defs task timeout
-        memory meta provers csv summary no_color output save wal_mode
+    let aux j cpus pp_results dyn paths dir_files proof_dir (log_lvl, defs) task
+        timeout memory meta provers csv summary no_color output save wal_mode
         desktop_notification no_failure update =
+      Misc.setup_logs log_lvl;
       catch_err @@ fun () ->
       if no_color then CCFormat.set_color_default false;
       let dyn =
@@ -173,10 +174,11 @@ module Slurm = struct
   (* sub-command for running tests with slurm *)
   let cmd =
     let open Cmdliner in
-    let aux j pp_results dyn paths dir_files proof_dir defs task timeout memory
-        meta provers csv summary no_color output save wal_mode
+    let aux j pp_results dyn paths dir_files proof_dir (log_lvl, defs) task
+        timeout memory meta provers csv summary no_color output save wal_mode
         desktop_notification no_failure update partition nodes addr port ntasks
         =
+      Misc.setup_logs log_lvl;
       catch_err @@ fun () ->
       if no_color then CCFormat.set_color_default false;
       let dyn =
@@ -543,7 +545,8 @@ end
 (** {2 See prover(s)} *)
 
 module Prover_show = struct
-  let run defs names =
+  let run (log_lvl, defs) names =
+    Misc.setup_logs log_lvl;
     catch_err @@ fun () ->
     let l = CCList.map (Definitions.find_prover' defs) names in
     Format.printf "@[<v>%a@]@." (Misc.pp_list Prover.pp) l;
@@ -561,7 +564,8 @@ end
 (** {2 List provers} *)
 
 module Prover_list = struct
-  let run defs =
+  let run (log_lvl, defs) =
+    Misc.setup_logs log_lvl;
     catch_err @@ fun () ->
     let l = Definitions.all_provers defs in
     Format.printf "@[<v>%a@]@."
@@ -580,7 +584,8 @@ end
 (** {2 Show Task} *)
 
 module Task_show = struct
-  let run defs names =
+  let run (log_lvl, defs) names =
+    Misc.setup_logs log_lvl;
     catch_err @@ fun () ->
     let l = CCList.map (Definitions.find_task' defs) names in
     Format.printf "@[<v>%a@]@." (Misc.pp_list Task.pp) l;
@@ -598,7 +603,8 @@ end
 (** {2 List Tasks} *)
 
 module Task_list = struct
-  let run defs =
+  let run (log_lvl, defs) =
+    Misc.setup_logs log_lvl;
     catch_err @@ fun () ->
     let l = Definitions.all_tasks defs in
     Format.printf "@[<v>%a@]@."
diff --git a/src/core/Bin_utils.ml b/src/core/Bin_utils.ml
index 70205e9..2a209e0 100644
--- a/src/core/Bin_utils.ml
+++ b/src/core/Bin_utils.ml
@@ -2,10 +2,9 @@ module T = Test
 module Db = Misc.Db
 module MStr = Misc.Str_map
 
-let definitions_term : Definitions.t Cmdliner.Term.t =
+let definitions_term : (Logs.level option * Definitions.t) Cmdliner.Term.t =
   let open Cmdliner in
   let aux conf_files with_default logs_cmd =
-    Misc.setup_logs logs_cmd;
     let conf_files = CCList.flatten conf_files in
     let conf_files =
       let default_conf = Misc.default_config () in
@@ -22,7 +21,7 @@ let definitions_term : Definitions.t Cmdliner.Term.t =
     try
       let stanzas = Stanza.parse_files conf_files in
       let defs = Definitions.add_stanza_l stanzas Definitions.empty in
-      `Ok defs
+      `Ok (logs_cmd, defs)
     with Error.E err -> `Error (false, Error.show err)
   in
   let args =
diff --git a/src/core/Prover.ml b/src/core/Prover.ml
index bdc841a..1bff507 100644
--- a/src/core/Prover.ml
+++ b/src/core/Prover.ml
@@ -347,7 +347,7 @@ let of_db db name : t =
         ~ty:Db.Ty.(p1 text, p2 any_str any_str, mkp2)
         ~f:Db.Cursor.to_list name
     with e ->
-      Log.err (fun k ->
+      Log.debug (fun k ->
           k "prover.of_db: could not find tags: %s" (Printexc.to_string e));
       []
   in
diff --git a/src/core/Test_detailed_res.ml b/src/core/Test_detailed_res.ml
index 43942a0..5f9c8a2 100644
--- a/src/core/Test_detailed_res.ml
+++ b/src/core/Test_detailed_res.ml
@@ -141,9 +141,8 @@ let get_res db prover file : _ * proof_check_res option =
               float;
               float;
             ],
-            fun x1 x2 x3 x4 x5 x6 x7 x8 x9 ->
-              Logs.info (fun k -> k "got results");
-              x1, x2, x3, x4, x5, x6, x7, x8, x9 ))
+            fun x1 x2 x3 x4 x5 x6 x7 x8 x9 -> x1, x2, x3, x4, x5, x6, x7, x8, x9
+          ))
     |> Misc.unwrap_db (fun () -> spf "listing results")
     |> Error.unwrap_opt' (fun () ->
            spf "expected a non-empty result for prover='%s', file='%s'" prover
@@ -157,7 +156,6 @@ let get_res db prover file : _ * proof_check_res option =
              rtime,
              utime,
              stime ) ->
-    Logs.info (fun k -> k "got results 2");
     let stdout = CCOpt.get_or ~default:"" stdout in
     let stderr = CCOpt.get_or ~default:"" stderr in
     Logs.debug (fun k -> k "res.of_string tags=[%s]" (String.concat "," tags));
@@ -171,9 +169,7 @@ let get_res db prover file : _ * proof_check_res option =
       { Run_proc_result.errcode; stdout; stderr; rtime; utime; stime }
   in
   let proof_check_res = get_proof_check db prover file in
-  Logs.info (fun k -> k "try to get prover");
   let prover = Prover.of_db db prover in
-  Logs.info (fun k -> k "got prover");
   Run_result.map ~f:(fun _ -> prover) res, proof_check_res
 
 module PB = PrintBox
diff --git a/src/core/Test_stat.ml b/src/core/Test_stat.ml
index 913577b..e56d83b 100644
--- a/src/core/Test_stat.ml
+++ b/src/core/Test_stat.ml
@@ -11,12 +11,7 @@ module Stats = struct
   let curr = snd
   let init = { n = 0; total = 0.; mean = 0., 0.; s = 0., 0. }
 
-  let step ({ n; total; mean; s } as acc) x =
-    let x =
-      match x with
-      | Sqlite3.Data.FLOAT f -> f
-      | _ -> assert false
-    in
+  let step ({ n; total; mean; s } as acc) (x : float) =
     let n = n + 1 in
     let total = total +. x in
     if n = 1 then
@@ -40,13 +35,6 @@ module Stats = struct
       0.
     else
       Float.(sqrt (s /. of_int (n - 1)))
-
-  let final acc =
-    let res = Fmt.asprintf "%f|%f|%f" (total acc) (mean acc) (sd acc) in
-    Sqlite3.Data.TEXT res
-
-  let attach_aggregate db =
-    Sqlite3.Aggregate.create_fun1 db ~init ~step ~final "stats"
 end
 
 type detail_stats = { n: int; total: float; mean: float; sd: float }
@@ -159,29 +147,35 @@ let to_printbox_l ?(details = false) ?to_link l : PB.t =
 let of_db_for ~(prover : Prover.name) (db : Db.t) : t =
   Error.guard (Error.wrapf "reading stat(%s) from DB" prover) @@ fun () ->
   let custom = Prover.tags_of_db db in
-  Stats.attach_aggregate db;
-  let convert n stats =
-    let extract_stats stats =
-      String.split_on_char '|' stats |> List.map Float.of_string |> function
-      | [ total; mean; sd ] ->
-        { n = CCOpt.get_or ~default:0 n; total; mean; sd }
-      | _ -> assert false
-    in
-    extract_stats stats
-  in
   let get_res r =
     Error.guard (Error.wrapf "get-res %S" r) @@ fun () ->
-    Logs.debug (fun k -> k "get-res %S" r);
-    Db.exec db
-      {| select count(*), stats(rtime) from prover_res where prover=? and res=?; |}
-      prover r
-      ~ty:Db.Ty.(p2 text text, p2 (nullable int) text, convert)
-      ~f:Db.Cursor.get_one_exn
-    |> Misc.unwrap_db (fun () -> spf "problems with result %s" r)
+    let count : int option =
+      Db.exec db {| select count(*) from prover_res where prover=? and res=?; |}
+        prover r
+        ~ty:Db.Ty.(p2 text text, p1 (nullable int), Fun.id)
+        ~f:Db.Cursor.get_one_exn
+      |> Misc.unwrap_db (fun () -> spf "problems with result %s" r)
+    in
+
+    let stats =
+      let stat = ref Stats.init in
+      Db.exec db {| select rtime from prover_res where prover=? and res=?; |}
+        prover r
+        ~ty:Db.Ty.(p2 text text, p1 float, Fun.id)
+        ~f:(fun cursor ->
+          Db.Cursor.iter cursor ~f:(fun rtime -> stat := Stats.step !stat rtime))
+      |> Misc.unwrap_db (fun () -> spf "problems with result %s" r);
+      !stat
+    in
+
+    let total = Stats.total stats in
+    let mean = Stats.mean stats in
+    let sd = Stats.sd stats in
+    { n = CCOpt.get_or ~default:0 count; total; mean; sd }
   in
+
   let get_proof_res r =
     Error.guard (Error.wrapf "get-proof-res %S %S" prover r) @@ fun () ->
-    Logs.debug (fun k -> k "get-proof-res %S %S" prover r);
     try
       Db.exec db
         {| select count( * ) from proof_check_res where prover=? and res=?; |}
diff --git a/src/server/benchpress_server.ml b/src/server/benchpress_server.ml
index f39905e..6e7a815 100644
--- a/src/server/benchpress_server.ml
+++ b/src/server/benchpress_server.ml
@@ -9,6 +9,36 @@ module Log = (val Logs.src_log (Logs.Src.create "benchpress-serve"))
 let spf = Printf.sprintf
 let[@inline] ( let@ ) f x = f x
 
+module Logger = struct
+  let show_lvl = function
+    | Logs.Debug -> "<7>DEBUG"
+    | Logs.Info -> "<6>INFO"
+    | Logs.Error -> "<3>ERROR"
+    | Logs.Warning -> "<4>WARNING"
+    | Logs.App -> "<5>APP"
+
+  let make_stdout () : Logs.reporter =
+    let app = Format.std_formatter in
+    let dst = Format.std_formatter in
+    let pp_header out (lvl, src) : unit =
+      let src =
+        match src with
+        | None -> ""
+        | Some s -> spf "[%s]" s
+      in
+      Fmt.fprintf out "%s%s: " (show_lvl lvl) src
+    in
+    Logs.format_reporter ~pp_header ~app ~dst ()
+
+  let setup (lvl : Logs.level option) =
+    let m = Mutex.create () in
+    Logs.set_reporter_mutex
+      ~lock:(fun () -> Mutex.lock m)
+      ~unlock:(fun () -> Mutex.unlock m);
+    Logs.set_level ~all:true lvl;
+    Logs.set_reporter @@ make_stdout ()
+end
+
 type expect_filter =
   | TD_expect_improved
   | TD_expect_ok
@@ -48,7 +78,7 @@ end = struct
 
   let attrs_of_style (s : B.Style.t) : _ list * _ =
     let open B.Style in
-    let { bold; bg_color; fg_color } = s in
+    let { bold; bg_color; fg_color; _ } = s in
     let encode_color = function
       | Red -> "red"
       | Blue -> "blue"
@@ -348,9 +378,9 @@ let handle_show (self : t) : unit =
     H.Route.(exact "show" @/ string_urlencoded @/ return)
   @@ fun file _req ->
   let@ chrono = query_wrap (Error.wrapf "serving %s" @@ uri_show file) in
-  Log.info (fun k -> k "----- start show %s -----" file);
+  Log.debug (fun k -> k "----- start show %s -----" file);
   let _file_full, cr = Bin_utils.load_file_summary ~full:false file in
-  Log.info (fun k ->
+  Log.debug (fun k ->
       k "show: loaded summary in %.3fs" (Misc.Chrono.since_last chrono));
   let box_meta =
     (* link to the prover locally *)
@@ -377,7 +407,7 @@ let handle_show (self : t) : unit =
   let uri_plot = uri_gnuplot file in
   let uri_err = uri_error_bad file in
   let uri_invalid = uri_invalid file in
-  Log.info (fun k ->
+  Log.debug (fun k ->
       k "rendered to PB in %.3fs" (Misc.Chrono.since_last chrono));
   let h =
     let open Html in
@@ -435,7 +465,7 @@ let handle_show (self : t) : unit =
             [ h3 [] [ txt "comparisons" ]; div [] [ pb_html box_compare_l ] ]);
       ]
   in
-  Log.info (fun k ->
+  Log.debug (fun k ->
       k "show: turned into html in %.3fs" (Misc.Chrono.since_last chrono));
   Log.debug (fun k -> k "show: successful reply for %S" file);
   H.Response.make_string ~headers:default_html_headers (Ok (Html.to_string h))
@@ -447,7 +477,7 @@ let handle_prover_in (self : t) : unit =
       exact "prover-in" @/ string_urlencoded @/ string_urlencoded @/ return)
   @@ fun file p_name _req ->
   let@ _chrono = query_wrap (Error.wrapf "prover-in-file/%s/%s" file p_name) in
-  Log.info (fun k -> k "----- start prover-in %s %s -----" file p_name);
+  Log.debug (fun k -> k "----- start prover-in %s %s -----" file p_name);
   let@ db =
     Bin_utils.with_file_as_db
       ~map_err:(Error.wrapf "reading file '%s'" file)
@@ -482,7 +512,7 @@ let handle_show_gp (self : t) : unit =
     H.Route.(exact "show-gp" @/ string_urlencoded @/ return)
   @@ fun q_arg _req ->
   let@ chrono = query_wrap (Error.wrapf "serving /show-gp/%s" q_arg) in
-  Log.info (fun k -> k "----- start show-gp %s -----" q_arg);
+  Log.debug (fun k -> k "----- start show-gp %s -----" q_arg);
   let files = CCString.split_on_char ',' q_arg |> List.map String.trim in
   let files_full =
     CCList.map
@@ -520,16 +550,16 @@ let handle_show_errors (self : t) : unit =
     H.Route.(exact "show-err" @/ string_urlencoded @/ return)
   @@ fun file _req ->
   let@ chrono = query_wrap (Error.wrapf "serving show-err/%s" file) in
-  Log.info (fun k -> k "----- start show-err %s -----" file);
+  Log.debug (fun k -> k "----- start show-err %s -----" file);
   let _file_full, cr = Bin_utils.load_file_summary ~full:true file in
-  Log.info (fun k ->
+  Log.debug (fun k ->
       k "show-err: loaded full summary in %.3fs" (Misc.Chrono.since_last chrono));
   let link_file = link_show_single file in
   let bad = Test_analyze.to_printbox_bad_l ~link:link_file cr.cr_analyze in
   let errors =
     Test_analyze.to_printbox_errors_l ~link:link_file cr.cr_analyze
   in
-  Log.info (fun k ->
+  Log.debug (fun k ->
       k "rendered to PB in %.3fs" (Misc.Chrono.since_last chrono));
   let mk_dl_file l =
     let open Html in
@@ -577,8 +607,8 @@ let handle_show_errors (self : t) : unit =
              errors);
       ]
   in
-  Log.info (fun k ->
-      k "show:turned into html in %.3fs" (Misc.Chrono.since_last chrono));
+  Log.debug (fun k ->
+      k "show: turned into html in %.3fs" (Misc.Chrono.since_last chrono));
   Log.debug (fun k -> k "successful reply for %S" file);
   H.Response.make_string (Ok (Html.to_string_elt h))
 
@@ -587,15 +617,16 @@ let handle_show_invalid (self : t) : unit =
     H.Route.(exact "show-invalid" @/ string_urlencoded @/ return)
   @@ fun file _req ->
   let@ chrono = query_wrap (Error.wrapf "serving show-invalid/%s" file) in
-  Log.info (fun k -> k "----- start show-invalid %s -----" file);
+  Log.debug (fun k -> k "----- start show-invalid %s -----" file);
   let _file_full, cr = Bin_utils.load_file_summary ~full:true file in
-  Log.info (fun k ->
-      k "show-err: loaded full summary in %.3fs" (Misc.Chrono.since_last chrono));
+  Log.debug (fun k ->
+      k "show-invalid: loaded full summary in %.3fs"
+        (Misc.Chrono.since_last chrono));
   let link_file = link_show_single file in
   let invalid =
     Test_analyze.to_printbox_invalid_proof_l ~link:link_file cr.cr_analyze
   in
-  Log.info (fun k ->
+  Log.debug (fun k ->
       k "rendered to PB in %.3fs" (Misc.Chrono.since_last chrono));
   let mk_dl_file l =
     let open Html in
@@ -626,8 +657,8 @@ let handle_show_invalid (self : t) : unit =
            ])
          invalid)
   in
-  Log.info (fun k ->
-      k "show:turned into html in %.3fs" (Misc.Chrono.since_last chrono));
+  Log.debug (fun k ->
+      k "show-info: turned into html in %.3fs" (Misc.Chrono.since_last chrono));
   Log.debug (fun k -> k "successful reply for %S" file);
   H.Response.make_string (Ok (Html.to_string_elt h))
 
@@ -669,7 +700,7 @@ let handle_show_as_table (self : t) : unit =
     Test_top_result.db_to_printbox_table ?filter_res ~filter_pb ~offset
       ~link_pb:link_get_file ~page_size ~link_res db
   in
-  Log.info (fun k ->
+  Log.debug (fun k ->
       k "loaded table[offset=%d] in %.3fs" offset
         (Misc.Chrono.since_last chrono));
   let h =
@@ -1601,7 +1632,7 @@ let handle_root (self : t) : unit =
           ];
       ]
   in
-  Log.info (fun k ->
+  Log.debug (fun k ->
       k "listed results in %.3fs" (Misc.Chrono.since_last chrono));
   Jemalloc.epoch ();
   H.Response.make_string ~headers:default_html_headers (Ok (Html.to_string h))
@@ -1627,7 +1658,7 @@ let handle_file_summary (self : t) : unit =
     H.Response.make_string ~headers:default_html_headers
       (Ok (Html.to_string_elt h))
   in
-  Log.info (fun k ->
+  Log.debug (fun k ->
       k "summary for %s in %.3fs" file (Misc.Chrono.since_last chrono));
   r
 
@@ -1675,8 +1706,10 @@ let handle_file self : unit =
 (** {2 Embedded web server} *)
 
 module Cmd = struct
-  let main ?(local_only = false) ?port ~allow_delete (defs : Definitions.t) () =
+  let main ?(local_only = false) ?port ~allow_delete ~log_lvl
+      (defs : Definitions.t) () =
     try
+      Logger.setup log_lvl;
       let addr =
         if local_only then
           "127.0.0.1"
@@ -1684,6 +1717,11 @@ module Cmd = struct
           "0.0.0.0"
       in
       let server = H.create ~max_connections:32 ~addr ?port () in
+
+      let prometheus = Tiny_httpd_prometheus.(global) in
+      Tiny_httpd_prometheus.instrument_server server prometheus;
+      Tiny_httpd_prometheus.GC_metrics.create_and_update_before_emit prometheus;
+
       let data_dir = Misc.data_dir () in
       let self =
         {
@@ -1697,10 +1735,6 @@ module Cmd = struct
       in
       (* thread to execute tasks *)
       let _th_r = Thread.create Task_queue.loop self.task_q in
-      (* trick: see if debug level is active *)
-      Log.debug (fun k ->
-          H._enable_debug true;
-          k "enable http debug");
       (* maybe serve the API *)
       Printf.printf "listen on http://localhost:%d/\n%!" (H.port server);
       handle_root self;
@@ -1743,8 +1777,8 @@ module Cmd = struct
         & info [ "allow-delete" ] ~doc:"allow deletion of files")
     and defs = Bin_utils.definitions_term in
     let doc = "serve embedded web UI on given port" in
-    let aux defs port local_only allow_delete () =
-      main ?port ~local_only ~allow_delete defs ()
+    let aux (log_lvl, defs) port local_only allow_delete () =
+      main ?port ~local_only ~allow_delete defs ~log_lvl ()
     in
     ( Term.(const aux $ defs $ port $ local_only $ allow_delete $ const ()),
       Cmd.info ~doc "serve" )
diff --git a/src/server/dune b/src/server/dune
index 1e0d4dd..e559d45 100644
--- a/src/server/dune
+++ b/src/server/dune
@@ -7,7 +7,7 @@
   (into ../../)
   (until-clean))
  (libraries benchpress containers cmdliner result uuidm logs logs.cli
-   tiny_httpd sqlite3_utils base64 printbox jemalloc)
+   tiny_httpd tiny_httpd.prometheus sqlite3_utils base64 printbox jemalloc)
  (flags :standard -warn-error -a+8 -safe-string -open Benchpress -linkall))
 
 (rule
diff --git a/src/worker/benchpress_worker.ml b/src/worker/benchpress_worker.ml
index de63b03..9704df9 100644
--- a/src/worker/benchpress_worker.ml
+++ b/src/worker/benchpress_worker.ml
@@ -1,6 +1,7 @@
 let parse_cmdline =
   let open Cmdliner in
-  let aux defs id socket_addr_opt socket_port j timeout memory =
+  let aux (log_lvl, defs) id socket_addr_opt socket_port j timeout memory =
+    Misc.setup_logs log_lvl;
     try
       let socket_addr =
         match socket_addr_opt with