refactor: better concurrency and use base highlight options

3 files changed, 437 insertions, 536 deletions

diff --git a/src/index.html b/src/index.html
index 8d89859..f5510a2 100644
--- a/src/index.html
+++ b/src/index.html
@@ -96,329 +96,7 @@
     <div class="controls"><button id="get-link-btn" type="button" title="generate snippet link">generate
             link</button><span class="spacer"></span><label><input type="checkbox" id="is-code">is this code?
         </label><select id="lang-select">
-            <option value="">auto-detect</option>
-            <option value="1c">1c</option>
-            <option value="abnf">abnf</option>
-            <option value="accesslog">accesslog</option>
-            <option value="actionscript">actionscript</option>
-            <option value="as">as</option>
-            <option value="ada">ada</option>
-            <option value="angelscript">angelscript</option>
-            <option value="asc">asc</option>
-            <option value="apache">apache</option>
-            <option value="apacheconf">apacheconf</option>
-            <option value="applescript">applescript</option>
-            <option value="osascript">osascript</option>
-            <option value="arcade">arcade</option>
-            <option value="arduino">arduino</option>
-            <option value="ino">ino</option>
-            <option value="armasm">armasm</option>
-            <option value="arm">arm</option>
-            <option value="asciidoc">asciidoc</option>
-            <option value="adoc">adoc</option>
-            <option value="aspectj">aspectj</option>
-            <option value="autohotkey">autohotkey</option>
-            <option value="autoit">autoit</option>
-            <option value="avrasm">avrasm</option>
-            <option value="awk">awk</option>
-            <option value="mawk">mawk</option>
-            <option value="nawk">nawk</option>
-            <option value="gawk">gawk</option>
-            <option value="ballerina">ballerina</option>
-            <option value="bal">bal</option>
-            <option value="bash">bash</option>
-            <option value="sh">sh</option>
-            <option value="zsh">zsh</option>
-            <option value="basic">basic</option>
-            <option value="bnf">bnf</option>
-            <option value="brainfuck">brainfuck</option>
-            <option value="bf">bf</option>
-            <option value="c">c</option>
-            <option value="h">h</option>
-            <option value="csharp">csharp</option>
-            <option value="cpp">cpp</option>
-            <option value="hpp">hpp</option>
-            <option value="cc">cc</option>
-            <option value="hh">hh</option>
-            <option value="c++">c++</option>
-            <option value="h++">h++</option>
-            <option value="cxx">cxx</option>
-            <option value="hxx">hxx</option>
-            <option value="cal">cal</option>
-            <option value="cos">cos</option>
-            <option value="cls">cls</option>
-            <option value="capnproto">capnproto</option>
-            <option value="capnp">capnp</option>
-            <option value="clojure">clojure</option>
-            <option value="clj">clj</option>
-            <option value="cmake">cmake</option>
-            <option value="cmake.in">cmake.in</option>
-            <option value="coffeescript">coffeescript</option>
-            <option value="coffee">coffee</option>
-            <option value="cson">cson</option>
-            <option value="iced">iced</option>
-            <option value="coq">coq</option>
-            <option value="crmsh">crmsh</option>
-            <option value="crm">crm</option>
-            <option value="pcmk">pcmk</option>
-            <option value="crystal">crystal</option>
-            <option value="cr">cr</option>
-            <option value="csp">csp</option>
-            <option value="css">css</option>
-            <option value="d">d</option>
-            <option value="dart">dart</option>
-            <option value="dpr">dpr</option>
-            <option value="dfm">dfm</option>
-            <option value="pas">pas</option>
-            <option value="pascal">pascal</option>
-            <option value="diff">diff</option>
-            <option value="patch">patch</option>
-            <option value="django">django</option>
-            <option value="jinja">jinja</option>
-            <option value="dns">dns</option>
-            <option value="zone">zone</option>
-            <option value="bind">bind</option>
-            <option value="dockerfile">dockerfile</option>
-            <option value="docker">docker</option>
-            <option value="dos">dos</option>
-            <option value="bat">bat</option>
-            <option value="cmd">cmd</option>
-            <option value="dsconfig">dsconfig</option>
-            <option value="dts">dts</option>
-            <option value="dust">dust</option>
-            <option value="dst">dst</option>
-            <option value="ebnf">ebnf</option>
-            <option value="elixir">elixir</option>
-            <option value="elm">elm</option>
-            <option value="erlang">erlang</option>
-            <option value="erl">erl</option>
-            <option value="excel">excel</option>
-            <option value="xls">xls</option>
-            <option value="xlsx">xlsx</option>
-            <option value="extempore">extempore</option>
-            <option value="xtlang">xtlang</option>
-            <option value="xtm">xtm</option>
-            <option value="fsharp">fsharp</option>
-            <option value="fs">fs</option>
-            <option value="fsx">fsx</option>
-            <option value="fsi">fsi</option>
-            <option value="fsscript">fsscript</option>
-            <option value="fix">fix</option>
-            <option value="fortran">fortran</option>
-            <option value="f90">f90</option>
-            <option value="f95">f95</option>
-            <option value="gcode">gcode</option>
-            <option value="nc">nc</option>
-            <option value="gams">gams</option>
-            <option value="gms">gms</option>
-            <option value="gauss">gauss</option>
-            <option value="gss">gss</option>
-            <option value="gherkin">gherkin</option>
-            <option value="go">go</option>
-            <option value="golang">golang</option>
-            <option value="golo">golo</option>
-            <option value="gololang">gololang</option>
-            <option value="gradle">gradle</option>
-            <option value="graphql">graphql</option>
-            <option value="gql">gql</option>
-            <option value="groovy">groovy</option>
-            <option value="haml">haml</option>
-            <option value="handlebars">handlebars</option>
-            <option value="hbs">hbs</option>
-            <option value="html.hbs">html.hbs</option>
-            <option value="html.handlebars">html.handlebars</option>
-            <option value="haskell">haskell</option>
-            <option value="hs">hs</option>
-            <option value="haxe">haxe</option>
-            <option value="hx">hx</option>
-            <option value="xml">xml</option>
-            <option value="html">html</option>
-            <option value="xhtml">xhtml</option>
-            <option value="rss">rss</option>
-            <option value="atom">atom</option>
-            <option value="xjb">xjb</option>
-            <option value="xsd">xsd</option>
-            <option value="xsl">xsl</option>
-            <option value="plist">plist</option>
-            <option value="svg">svg</option>
-            <option value="http">http</option>
-            <option value="https">https</option>
-            <option value="hy">hy</option>
-            <option value="hylang">hylang</option>
-            <option value="inform7">inform7</option>
-            <option value="i7">i7</option>
-            <option value="ini">ini</option>
-            <option value="toml">toml</option>
-            <option value="irpf90">irpf90</option>
-            <option value="java">java</option>
-            <option value="jsp">jsp</option>
-            <option value="javascript">javascript</option>
-            <option value="js">js</option>
-            <option value="jsx">jsx</option>
-            <option value="json">json</option>
-            <option value="jsonc">jsonc</option>
-            <option value="json5">json5</option>
-            <option value="julia">julia</option>
-            <option value="jl">jl</option>
-            <option value="julia-repl">julia-repl</option>
-            <option value="kotlin">kotlin</option>
-            <option value="kt">kt</option>
-            <option value="lasso">lasso</option>
-            <option value="lassoscript">lassoscript</option>
-            <option value="tex">tex</option>
-            <option value="ldif">ldif</option>
-            <option value="leaf">leaf</option>
-            <option value="less">less</option>
-            <option value="lisp">lisp</option>
-            <option value="livecodeserver">livecodeserver</option>
-            <option value="livescript">livescript</option>
-            <option value="lua">lua</option>
-            <option value="pluto">pluto</option>
-            <option value="makefile">makefile</option>
-            <option value="mk">mk</option>
-            <option value="mak">mak</option>
-            <option value="make">make</option>
-            <option value="markdown">markdown</option>
-            <option value="md">md</option>
-            <option value="mkdown">mkdown</option>
-            <option value="mkd">mkd</option>
-            <option value="mathematica">mathematica</option>
-            <option value="mma">mma</option>
-            <option value="wl">wl</option>
-            <option value="matlab">matlab</option>
-            <option value="maxima">maxima</option>
-            <option value="mel">mel</option>
-            <option value="mercury">mercury</option>
-            <option value="mips">mips</option>
-            <option value="mipsasm">mipsasm</option>
-            <option value="mizar">mizar</option>
-            <option value="mojolicious">mojolicious</option>
-            <option value="monkey">monkey</option>
-            <option value="moonscript">moonscript</option>
-            <option value="moon">moon</option>
-            <option value="n1ql">n1ql</option>
-            <option value="nginx">nginx</option>
-            <option value="nginxconf">nginxconf</option>
-            <option value="nim">nim</option>
-            <option value="nimrod">nimrod</option>
-            <option value="nix">nix</option>
-            <option value="nsis">nsis</option>
-            <option value="objectivec">objectivec</option>
-            <option value="mm">mm</option>
-            <option value="objc">objc</option>
-            <option value="obj-c">obj-c</option>
-            <option value="obj-c++">obj-c++</option>
-            <option value="objective-c++">objective-c++</option>
-            <option value="ocaml">ocaml</option>
-            <option value="glsl">glsl</option>
-            <option value="openscad">openscad</option>
-            <option value="scad">scad</option>
-            <option value="ruleslanguage">ruleslanguage</option>
-            <option value="oxygene">oxygene</option>
-            <option value="parser3">parser3</option>
-            <option value="perl">perl</option>
-            <option value="pl">pl</option>
-            <option value="pm">pm</option>
-            <option value="pf">pf</option>
-            <option value="pf.conf">pf.conf</option>
-            <option value="php">php</option>
-            <option value="plaintext">plaintext</option>
-            <option value="txt">txt</option>
-            <option value="text">text</option>
-            <option value="pony">pony</option>
-            <option value="pgsql">pgsql</option>
-            <option value="postgres">postgres</option>
-            <option value="postgresql">postgresql</option>
-            <option value="powershell">powershell</option>
-            <option value="ps">ps</option>
-            <option value="ps1">ps1</option>
-            <option value="processing">processing</option>
-            <option value="prolog">prolog</option>
-            <option value="properties">properties</option>
-            <option value="proto">proto</option>
-            <option value="protobuf">protobuf</option>
-            <option value="puppet">puppet</option>
-            <option value="pp">pp</option>
-            <option value="python">python</option>
-            <option value="py">py</option>
-            <option value="gyp">gyp</option>
-            <option value="profile">profile</option>
-            <option value="python-repl">python-repl</option>
-            <option value="pycon">pycon</option>
-            <option value="k">k</option>
-            <option value="kdb">kdb</option>
-            <option value="qml">qml</option>
-            <option value="r">r</option>
-            <option value="reasonml">reasonml</option>
-            <option value="rib">rib</option>
-            <option value="rsl">rsl</option>
-            <option value="graph">graph</option>
-            <option value="instances">instances</option>
-            <option value="ruby">ruby</option>
-            <option value="rb">rb</option>
-            <option value="gemspec">gemspec</option>
-            <option value="podspec">podspec</option>
-            <option value="thor">thor</option>
-            <option value="irb">irb</option>
-            <option value="rust">rust</option>
-            <option value="rs">rs</option>
-            <option value="sas">sas</option>
-            <option value="scala">scala</option>
-            <option value="scheme">scheme</option>
-            <option value="scilab">scilab</option>
-            <option value="sci">sci</option>
-            <option value="scss">scss</option>
-            <option value="shell">shell</option>
-            <option value="console">console</option>
-            <option value="smali">smali</option>
-            <option value="smalltalk">smalltalk</option>
-            <option value="st">st</option>
-            <option value="sml">sml</option>
-            <option value="sql">sql</option>
-            <option value="stan">stan</option>
-            <option value="stanfuncs">stanfuncs</option>
-            <option value="stata">stata</option>
-            <option value="p21">p21</option>
-            <option value="step">step</option>
-            <option value="stp">stp</option>
-            <option value="stylus">stylus</option>
-            <option value="styl">styl</option>
-            <option value="subunit">subunit</option>
-            <option value="swift">swift</option>
-            <option value="tcl">tcl</option>
-            <option value="tk">tk</option>
-            <option value="tap">tap</option>
-            <option value="thrift">thrift</option>
-            <option value="tp">tp</option>
-            <option value="twig">twig</option>
-            <option value="craftcms">craftcms</option>
-            <option value="typescript">typescript</option>
-            <option value="ts">ts</option>
-            <option value="tsx">tsx</option>
-            <option value="mts">mts</option>
-            <option value="cts">cts</option>
-            <option value="vala">vala</option>
-            <option value="vbnet">vbnet</option>
-            <option value="vb">vb</option>
-            <option value="vbscript">vbscript</option>
-            <option value="vbs">vbs</option>
-            <option value="verilog">verilog</option>
-            <option value="v">v</option>
-            <option value="vhdl">vhdl</option>
-            <option value="vim">vim</option>
-            <option value="axapta">axapta</option>
-            <option value="x++">x++</option>
-            <option value="x86asm">x86asm</option>
-            <option value="xl">xl</option>
-            <option value="tao">tao</option>
-            <option value="xquery">xquery</option>
-            <option value="xpath">xpath</option>
-            <option value="xq">xq</option>
-            <option value="xqm">xqm</option>
-            <option value="yml">yml</option>
-            <option value="yaml">yaml</option>
-            <option value="zephir">zephir</option>
-            <option value="zep">zep</option>
+            <option value="">(auto)</option>
         </select></div><br><input type="password" id="passphrase" autocomplete="off"
         placeholder="passphrase (optional)"><small>&nbsp;encrypted with <a href="https://github.com/kj-sh604/mojicrypt"
             target="_blank" rel="noopener noreferrer">mojicrypt</a></small>
diff --git a/src/main.js b/src/main.js
index 1f1b755..e0a9600 100644
--- a/src/main.js
+++ b/src/main.js
@@ -1,5 +1,223 @@
 const FORM_STATE_KEY = "kj-clipboard-form-state-v1";
 
+const HIGHLIGHTJS_LANGUAGES = [
+    "1c",
+    "abnf",
+    "accesslog",
+    "actionscript",
+    "ada",
+    "angelscript",
+    "apache",
+    "applescript",
+    "arcade",
+    "arduino",
+    "armasm",
+    "xml",
+    "asciidoc",
+    "aspectj",
+    "autohotkey",
+    "autoit",
+    "avrasm",
+    "awk",
+    "axapta",
+    "bash",
+    "basic",
+    "bnf",
+    "brainfuck",
+    "c",
+    "cal",
+    "capnproto",
+    "ceylon",
+    "clean",
+    "clojure",
+    "clojure-repl",
+    "cmake",
+    "coffeescript",
+    "coq",
+    "cos",
+    "cpp",
+    "crmsh",
+    "crystal",
+    "csharp",
+    "csp",
+    "css",
+    "d",
+    "markdown",
+    "dart",
+    "delphi",
+    "diff",
+    "django",
+    "dns",
+    "dockerfile",
+    "dos",
+    "dsconfig",
+    "dts",
+    "dust",
+    "ebnf",
+    "elixir",
+    "elm",
+    "ruby",
+    "erb",
+    "erlang-repl",
+    "erlang",
+    "excel",
+    "fix",
+    "flix",
+    "fortran",
+    "fsharp",
+    "gams",
+    "gauss",
+    "gcode",
+    "gherkin",
+    "glsl",
+    "gml",
+    "go",
+    "golo",
+    "gradle",
+    "graphql",
+    "groovy",
+    "haml",
+    "handlebars",
+    "haskell",
+    "haxe",
+    "hsp",
+    "http",
+    "hy",
+    "inform7",
+    "ini",
+    "irpf90",
+    "isbl",
+    "java",
+    "javascript",
+    "jboss-cli",
+    "json",
+    "julia",
+    "julia-repl",
+    "kotlin",
+    "lasso",
+    "latex",
+    "ldif",
+    "leaf",
+    "less",
+    "lisp",
+    "livecodeserver",
+    "livescript",
+    "llvm",
+    "lsl",
+    "lua",
+    "makefile",
+    "mathematica",
+    "matlab",
+    "maxima",
+    "mel",
+    "mercury",
+    "mipsasm",
+    "mizar",
+    "perl",
+    "mojolicious",
+    "monkey",
+    "moonscript",
+    "n1ql",
+    "nestedtext",
+    "nginx",
+    "nim",
+    "nix",
+    "node-repl",
+    "nsis",
+    "objectivec",
+    "ocaml",
+    "openscad",
+    "oxygene",
+    "parser3",
+    "pf",
+    "pgsql",
+    "php",
+    "php-template",
+    "plaintext",
+    "pony",
+    "powershell",
+    "processing",
+    "profile",
+    "prolog",
+    "properties",
+    "protobuf",
+    "puppet",
+    "purebasic",
+    "python",
+    "python-repl",
+    "q",
+    "qml",
+    "r",
+    "reasonml",
+    "rib",
+    "roboconf",
+    "routeros",
+    "rsl",
+    "ruleslanguage",
+    "rust",
+    "sas",
+    "scala",
+    "scheme",
+    "scilab",
+    "scss",
+    "shell",
+    "smali",
+    "smalltalk",
+    "sml",
+    "sqf",
+    "sql",
+    "stan",
+    "stata",
+    "step21",
+    "stylus",
+    "subunit",
+    "swift",
+    "taggerscript",
+    "yaml",
+    "tap",
+    "tcl",
+    "thrift",
+    "tp",
+    "twig",
+    "typescript",
+    "vala",
+    "vbnet",
+    "vbscript",
+    "vbscript-html",
+    "verilog",
+    "vhdl",
+    "vim",
+    "wasm",
+    "wren",
+    "x86asm",
+    "xl",
+    "xquery",
+    "zephir",
+];
+
+function syncLanguageOptions() {
+    const langSelect = document.getElementById("lang-select");
+    const selected = langSelect.value;
+
+    langSelect.innerHTML = "";
+
+    const autoOption = document.createElement("option");
+    autoOption.value = "";
+    autoOption.textContent = "(auto)";
+    langSelect.appendChild(autoOption);
+
+    for (const language of HIGHLIGHTJS_LANGUAGES) {
+        const option = document.createElement("option");
+        option.value = language;
+        option.textContent = language;
+        langSelect.appendChild(option);
+    }
+
+    if (selected && HIGHLIGHTJS_LANGUAGES.includes(selected)) {
+        langSelect.value = selected;
+    }
+}
+
 function saveFormState() {
     const state = {
         content: document.getElementById("content").value,
@@ -110,6 +328,7 @@ function setStatus(msg) {
     document.getElementById("status").textContent = msg;
 }
 
+syncLanguageOptions();
 restoreFormState();
 
 document.getElementById("get-link-btn").addEventListener("click", createPaste);
diff --git a/src/server.py b/src/server.py
index bddee31..303c1bf 100644
--- a/src/server.py
+++ b/src/server.py
@@ -7,6 +7,7 @@
 import http.server
 import json
 import ipaddress
+import queue
 import re
 import secrets
 import signal
@@ -52,6 +53,14 @@ SQLITE_SYNCHRONOUS = "NORMAL"  # OFF | NORMAL | FULL | EXTRA
 # accept short bursts without immediately refusing tcp connections.
 HTTP_REQUEST_QUEUE_SIZE = 64
 
+# single sqlite writer with queue + micro-batching reduces lock contention under load.
+WRITE_QUEUE_MAX_SIZE = 4096
+WRITE_QUEUE_WAIT_SECONDS = 8
+WRITE_QUEUE_ENQUEUE_TIMEOUT_SECONDS = 0.25
+WRITE_BATCH_SIZE = 32
+WRITE_BATCH_MAX_DELAY_MS = 12
+WRITE_WORKER_JOIN_TIMEOUT_SECONDS = 5
+
 TRUST_PROXY = False
 TRUSTED_PROXY_IPS = {"127.0.0.1", "::1"}
 # hsts off by default to avoid breaking plain-http setups.
@@ -63,324 +72,194 @@ ALLOWED_LANGUAGES = {
     "abnf",
     "accesslog",
     "actionscript",
-    "as",
     "ada",
     "angelscript",
-    "asc",
     "apache",
-    "apacheconf",
     "applescript",
-    "osascript",
     "arcade",
     "arduino",
-    "ino",
     "armasm",
-    "arm",
+    "xml",
     "asciidoc",
-    "adoc",
     "aspectj",
     "autohotkey",
     "autoit",
     "avrasm",
     "awk",
-    "mawk",
-    "nawk",
-    "gawk",
-    "ballerina",
-    "bal",
+    "axapta",
     "bash",
-    "sh",
-    "zsh",
     "basic",
     "bnf",
     "brainfuck",
-    "bf",
     "c",
-    "h",
-    "csharp",
-    "cpp",
-    "hpp",
-    "cc",
-    "hh",
-    "c++",
-    "h++",
-    "cxx",
-    "hxx",
     "cal",
-    "cos",
-    "cls",
     "capnproto",
-    "capnp",
+    "ceylon",
+    "clean",
     "clojure",
-    "clj",
+    "clojure-repl",
     "cmake",
-    "cmake.in",
     "coffeescript",
-    "coffee",
-    "cson",
-    "iced",
     "coq",
+    "cos",
+    "cpp",
     "crmsh",
-    "crm",
-    "pcmk",
     "crystal",
-    "cr",
+    "csharp",
     "csp",
     "css",
     "d",
+    "markdown",
     "dart",
-    "dpr",
-    "dfm",
-    "pas",
-    "pascal",
+    "delphi",
     "diff",
-    "patch",
     "django",
-    "jinja",
     "dns",
-    "zone",
-    "bind",
     "dockerfile",
-    "docker",
     "dos",
-    "bat",
-    "cmd",
     "dsconfig",
     "dts",
     "dust",
-    "dst",
     "ebnf",
     "elixir",
     "elm",
+    "ruby",
+    "erb",
+    "erlang-repl",
     "erlang",
-    "erl",
     "excel",
-    "xls",
-    "xlsx",
-    "extempore",
-    "xtlang",
-    "xtm",
-    "fsharp",
-    "fs",
-    "fsx",
-    "fsi",
-    "fsscript",
     "fix",
+    "flix",
+    "fsharp",
     "fortran",
-    "f90",
-    "f95",
     "gcode",
-    "nc",
     "gams",
-    "gms",
     "gauss",
-    "gss",
     "gherkin",
+    "glsl",
+    "gml",
     "go",
-    "golang",
     "golo",
-    "gololang",
     "gradle",
     "graphql",
-    "gql",
     "groovy",
     "haml",
     "handlebars",
-    "hbs",
-    "html.hbs",
-    "html.handlebars",
     "haskell",
-    "hs",
     "haxe",
-    "hx",
-    "xml",
-    "html",
-    "xhtml",
-    "rss",
-    "atom",
-    "xjb",
-    "xsd",
-    "xsl",
-    "plist",
-    "svg",
+    "hsp",
     "http",
-    "https",
     "hy",
-    "hylang",
     "inform7",
-    "i7",
     "ini",
-    "toml",
     "irpf90",
+    "isbl",
     "java",
-    "jsp",
     "javascript",
-    "js",
-    "jsx",
+    "jboss-cli",
     "json",
-    "jsonc",
-    "json5",
     "julia",
-    "jl",
     "julia-repl",
     "kotlin",
-    "kt",
     "lasso",
-    "lassoscript",
-    "tex",
+    "latex",
     "ldif",
     "leaf",
     "less",
     "lisp",
     "livecodeserver",
     "livescript",
+    "llvm",
+    "lsl",
     "lua",
-    "pluto",
     "makefile",
-    "mk",
-    "mak",
-    "make",
-    "markdown",
-    "md",
-    "mkdown",
-    "mkd",
     "mathematica",
-    "mma",
-    "wl",
     "matlab",
     "maxima",
     "mel",
     "mercury",
-    "mips",
     "mipsasm",
     "mizar",
+    "perl",
     "mojolicious",
     "monkey",
     "moonscript",
-    "moon",
     "n1ql",
+    "nestedtext",
     "nginx",
-    "nginxconf",
     "nim",
-    "nimrod",
     "nix",
+    "node-repl",
     "nsis",
     "objectivec",
-    "mm",
-    "objc",
-    "obj-c",
-    "obj-c++",
-    "objective-c++",
     "ocaml",
-    "glsl",
     "openscad",
-    "scad",
-    "ruleslanguage",
     "oxygene",
     "parser3",
-    "perl",
-    "pl",
-    "pm",
     "pf",
-    "pf.conf",
+    "pgsql",
     "php",
+    "php-template",
     "plaintext",
-    "txt",
-    "text",
     "pony",
-    "pgsql",
-    "postgres",
-    "postgresql",
     "powershell",
-    "ps",
-    "ps1",
     "processing",
     "prolog",
     "properties",
-    "proto",
     "protobuf",
     "puppet",
-    "pp",
+    "purebasic",
     "python",
-    "py",
-    "gyp",
     "profile",
     "python-repl",
-    "pycon",
-    "k",
-    "kdb",
+    "q",
     "qml",
     "r",
     "reasonml",
     "rib",
+    "roboconf",
+    "routeros",
     "rsl",
-    "graph",
-    "instances",
-    "ruby",
-    "rb",
-    "gemspec",
-    "podspec",
-    "thor",
-    "irb",
+    "ruleslanguage",
     "rust",
-    "rs",
     "sas",
     "scala",
     "scheme",
     "scilab",
-    "sci",
     "scss",
     "shell",
-    "console",
     "smali",
     "smalltalk",
-    "st",
     "sml",
+    "sqf",
     "sql",
     "stan",
-    "stanfuncs",
     "stata",
-    "p21",
-    "step",
-    "stp",
+    "step21",
     "stylus",
-    "styl",
     "subunit",
     "swift",
-    "tcl",
-    "tk",
+    "taggerscript",
+    "yaml",
     "tap",
+    "tcl",
     "thrift",
     "tp",
     "twig",
-    "craftcms",
     "typescript",
-    "ts",
-    "tsx",
-    "mts",
-    "cts",
     "vala",
     "vbnet",
-    "vb",
     "vbscript",
-    "vbs",
+    "vbscript-html",
     "verilog",
-    "v",
     "vhdl",
     "vim",
-    "axapta",
-    "x++",
+    "wasm",
+    "wren",
     "x86asm",
     "xl",
-    "tao",
     "xquery",
-    "xpath",
-    "xq",
-    "xqm",
-    "yml",
-    "yaml",
     "zephir",
-    "zep",
 
 }
 
@@ -389,6 +268,10 @@ ALLOWED_LANGUAGES = {
 _rate_lock = threading.Lock()
 _rate_state = {}
 
+_write_queue = queue.Queue(maxsize=WRITE_QUEUE_MAX_SIZE)
+_write_worker_thread = None
+_write_worker_stop = threading.Event()
+
 
 # database
 
@@ -408,6 +291,147 @@ def sqlite_retry_sleep(attempt):
     time.sleep(min((delay_ms + jitter_ms) / 1000.0, 1.0))
 
 
+def build_write_job(content, language, is_code, is_encrypted):
+    return {
+        "content": content,
+        "language": language,
+        "is_code": int(is_code),
+        "is_encrypted": int(is_encrypted),
+        "created_at": int(time.time()),
+        "paste_id": None,
+        "error": None,
+        "done": threading.Event(),
+    }
+
+
+def execute_write_batch(conn, jobs):
+    for write_attempt in range(SQLITE_WRITE_RETRIES + 1):
+        try:
+            conn.execute("BEGIN IMMEDIATE")
+            for job in jobs:
+                for _ in range(5):
+                    paste_id = generate_id()
+                    try:
+                        conn.execute(
+                            "INSERT INTO pastes (id, content, language, is_code, is_encrypted, created_at) "
+                            "VALUES (?, ?, ?, ?, ?, ?)",
+                            (
+                                paste_id,
+                                job["content"],
+                                job["language"],
+                                job["is_code"],
+                                job["is_encrypted"],
+                                job["created_at"],
+                            ),
+                        )
+                        job["paste_id"] = paste_id
+                        break
+                    except sqlite3.IntegrityError:
+                        continue
+                if not job["paste_id"]:
+                    raise RuntimeError("failed to generate unique paste id")
+
+            conn.commit()
+            return
+        except sqlite3.OperationalError as err:
+            try:
+                conn.rollback()
+            except sqlite3.DatabaseError:
+                pass
+
+            if is_sqlite_busy_error(err):
+                if write_attempt >= SQLITE_WRITE_RETRIES:
+                    raise DatabaseBusyError("database is busy; retry shortly") from err
+                sqlite_retry_sleep(write_attempt)
+                continue
+
+            raise
+        except Exception:
+            try:
+                conn.rollback()
+            except sqlite3.DatabaseError:
+                pass
+            raise
+
+
+def flush_write_batch(conn, jobs):
+    try:
+        execute_write_batch(conn, jobs)
+    except Exception as err:
+        for job in jobs:
+            job["error"] = err
+            job["done"].set()
+        return
+
+    for job in jobs:
+        job["done"].set()
+
+
+def collect_write_batch(first_job):
+    jobs = [first_job]
+    deadline = time.monotonic() + (WRITE_BATCH_MAX_DELAY_MS / 1000.0)
+
+    while len(jobs) < WRITE_BATCH_SIZE:
+        remaining = deadline - time.monotonic()
+        if remaining <= 0:
+            break
+
+        try:
+            next_job = _write_queue.get(timeout=remaining)
+        except queue.Empty:
+            break
+
+        jobs.append(next_job)
+
+    return jobs
+
+
+def write_worker_loop():
+    conn = open_db()
+    try:
+        while True:
+            if _write_worker_stop.is_set() and _write_queue.empty():
+                break
+
+            try:
+                first_job = _write_queue.get(timeout=0.25)
+            except queue.Empty:
+                continue
+
+            jobs = collect_write_batch(first_job)
+            flush_write_batch(conn, jobs)
+            for _ in jobs:
+                _write_queue.task_done()
+    finally:
+        conn.close()
+
+
+def start_write_worker():
+    global _write_worker_thread
+
+    if _write_worker_thread and _write_worker_thread.is_alive():
+        return
+
+    _write_worker_stop.clear()
+    _write_worker_thread = threading.Thread(
+        target=write_worker_loop,
+        daemon=True,
+        name="sqlite-write-worker",
+    )
+    _write_worker_thread.start()
+
+
+def stop_write_worker():
+    global _write_worker_thread
+
+    if not _write_worker_thread:
+        return
+
+    _write_worker_stop.set()
+    _write_worker_thread.join(timeout=WRITE_WORKER_JOIN_TIMEOUT_SECONDS)
+    _write_worker_thread = None
+
+
 def open_db():
     conn = sqlite3.connect(
         str(DB_PATH),
@@ -465,47 +489,25 @@ def is_valid_paste_id(paste_id):
 
 def save_paste(content, language=None, is_code=False, is_encrypted=False):
     """store a paste in the database, return its id"""
-    for write_attempt in range(SQLITE_WRITE_RETRIES + 1):
-        conn = open_db()
-        try:
-            # reserve the write lock early to reduce lock thrash under bursty writes.
-            conn.execute("BEGIN IMMEDIATE")
-            for _ in range(5):
-                paste_id = generate_id()
-                try:
-                    conn.execute(
-                        "INSERT INTO pastes (id, content, language, is_code, is_encrypted, created_at) "
-                        "VALUES (?, ?, ?, ?, ?, ?)",
-                        (
-                            paste_id,
-                            content,
-                            language,
-                            int(is_code),
-                            int(is_encrypted),
-                            int(time.time()),
-                        ),
-                    )
-                    conn.commit()
-                    return paste_id
-                except sqlite3.IntegrityError:
-                    continue
-            conn.rollback()
-            raise RuntimeError("failed to generate unique paste id")
-        except sqlite3.OperationalError as err:
-            try:
-                conn.rollback()
-            except sqlite3.DatabaseError:
-                pass
-            if is_sqlite_busy_error(err):
-                if write_attempt >= SQLITE_WRITE_RETRIES:
-                    raise DatabaseBusyError("database is busy; retry shortly") from err
-                sqlite_retry_sleep(write_attempt)
-                continue
-            raise
-        finally:
-            conn.close()
+    job = build_write_job(content, language, is_code, is_encrypted)
 
-    raise DatabaseBusyError("database is busy; retry shortly")
+    try:
+        _write_queue.put(job, timeout=WRITE_QUEUE_ENQUEUE_TIMEOUT_SECONDS)
+    except queue.Full as err:
+        raise DatabaseBusyError("write queue is full; retry shortly") from err
+
+    if not job["done"].wait(WRITE_QUEUE_WAIT_SECONDS):
+        raise DatabaseBusyError("write queue timeout; retry shortly")
+
+    if job["error"]:
+        if isinstance(job["error"], Exception):
+            raise job["error"]
+        raise RuntimeError("write failed")
+
+    if not job["paste_id"]:
+        raise RuntimeError("write completed without paste id")
+
+    return job["paste_id"]
 
 
 def get_paste(paste_id):
@@ -672,8 +674,8 @@ def paste_page(paste, csp_nonce):
     highlight_css = ""
     highlight_js = ""
     if is_code:
-        highlight_css = '<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/styles/vs2015.min.css">'
-        highlight_js = f"""<script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/highlight.min.js"></script>
+        highlight_css = '<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.11.1/styles/vs2015.min.css">'
+        highlight_js = f"""<script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.11.1/highlight.min.js"></script>
     <script{script_nonce_attr}>hljs.highlightAll();</script>"""
 
     return f"""<!DOCTYPE html>
@@ -1222,6 +1224,7 @@ class ClipboardHTTPServer(http.server.ThreadingHTTPServer):
 
 def main():
     init_db()
+    start_write_worker()
     print(f"kj-clipboard - listening on {BIND}:{PORT}")
 
     server = ClipboardHTTPServer((BIND, PORT), ClipboardHandler)
@@ -1245,6 +1248,7 @@ def main():
     except KeyboardInterrupt:
         print("\nreceived keyboard interrupt, shutting down.")
     finally:
+        stop_write_worker()
         server.server_close()