diff --git a/.gitignore b/.gitignore
index 4bef9b7513b..b8450316fdd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -210,3 +210,6 @@ curriculum/build
 ### Playwright ###
 
 /playwright
+
+### Shadow Testing Log Files Folder ###
+api/logs/
diff --git a/api/src/app.ts b/api/src/app.ts
index 120be3c1444..a41fa566dd3 100644
--- a/api/src/app.ts
+++ b/api/src/app.ts
@@ -27,6 +27,8 @@ import bouncer from './plugins/bouncer';
 import errorHandling from './plugins/error-handling';
 import csrf from './plugins/csrf';
 import notFound from './plugins/not-found';
+import shadowCapture from './plugins/shadow-capture';
+
 import * as publicRoutes from './routes/public';
 import * as protectedRoutes from './routes/protected';
 
@@ -35,6 +37,7 @@ import {
   EMAIL_PROVIDER,
   FCC_ENABLE_DEV_LOGIN_MODE,
   FCC_ENABLE_SWAGGER_UI,
+  FCC_ENABLE_SHADOW_CAPTURE,
   FREECODECAMP_NODE_ENV
 } from './utils/env';
 import { isObjectID } from './utils/validation';
@@ -127,6 +130,10 @@ export const build = async (
     fastify.log.info(`Swagger UI available at ${API_LOCATION}/documentation`);
   }
 
+  if (FCC_ENABLE_SHADOW_CAPTURE) {
+    void fastify.register(shadowCapture);
+  }
+
   void fastify.register(auth);
   void fastify.register(notFound);
   void fastify.register(prismaPlugin);
diff --git a/api/src/plugins/shadow-capture.ts b/api/src/plugins/shadow-capture.ts
new file mode 100644
index 00000000000..1fd74f5eca7
--- /dev/null
+++ b/api/src/plugins/shadow-capture.ts
@@ -0,0 +1,137 @@
+import { randomUUID } from 'crypto';
+import { appendFileSync, mkdirSync } from 'fs';
+import { join } from 'path';
+import type { FastifyPluginCallback } from 'fastify';
+
+import fp from 'fastify-plugin';
+import { FastifyReply } from 'fastify/types/reply';
+import { FastifyRequest } from 'fastify/types/request';
+
+const LOGS_DIRECTORY = 'logs';
+const REQUEST_CAPTURE_FILE = 'request-capture.jsonl';
+const RESPONSE_CAPTURE_FILE = 'response-capture.jsonl';
+
+let REQUEST_BUFFER: unknown[] = [];
+let RESPONSE_BUFFER: unknown[] = [];
+
+/**
+ * Plugin for capturing requests and responses to allow shadow testing.
+ *
+ * @param fastify The Fastify instance.
+ * @param _options Options passed to the plugin via `fastify.register(plugin, options)`.
+ * @param done Callback to signal that the logic has completed.
+ */
+const shadowCapture: FastifyPluginCallback = (fastify, _options, done) => {
+  mkdirSync(LOGS_DIRECTORY, { recursive: true });
+  fastify.addHook('onRequest', (req, rep, done) => {
+    // Attach timestamp at beginning of lifecycle
+    // @ts-expect-error Exists
+    req.__timestamp = Date.now();
+
+    // Give request and response same id to match.
+    const id = randomUUID();
+    // @ts-expect-error Exists
+    req.__id = id;
+    // @ts-expect-error Exists
+    rep.__id = id;
+    done();
+  });
+
+  // Body is only included after `Parsing` lifecycle
+  fastify.addHook('preValidation', (req, rep, done) => {
+    captureRequest(req);
+    done();
+  });
+
+  fastify.addHook('onSend', async (_req, rep, payload) => {
+    // @ts-expect-error Exists
+    rep.__payload = payload;
+    return payload;
+  });
+
+  fastify.addHook('onResponse', (_req, rep, done) => {
+    captureReply(rep);
+    done();
+  });
+
+  done();
+};
+
+/* eslint-disable @typescript-eslint/no-unsafe-assignment,@typescript-eslint/no-unsafe-return */
+function captureRequest(req: FastifyRequest) {
+  const savedRequest = {
+    // @ts-expect-error Exists
+    id: req.__id,
+    // @ts-expect-error Exists
+    timestamp: req.__timestamp,
+    url: req.url,
+    headers: omit(req.headers, 'cookie'),
+    cookies: include(req.cookies, '_csrf', 'csrf_token', 'jwt_access_token'),
+    user: req.user,
+    body: req.body
+  };
+
+  if (REQUEST_BUFFER.length > 10) {
+    appendFileSync(
+      join(LOGS_DIRECTORY, REQUEST_CAPTURE_FILE),
+      REQUEST_BUFFER.map(rb => JSON.stringify(rb)).join('\n') + '\n'
+    );
+    REQUEST_BUFFER = [savedRequest];
+  } else {
+    REQUEST_BUFFER.push(savedRequest);
+  }
+}
+
+function captureReply(rep: FastifyReply) {
+  const savedReply = {
+    // @ts-expect-error Exists
+    id: rep.__id,
+    headers: rep.getHeaders(),
+    timestamp: Date.now(),
+    // @ts-expect-error Exists
+    payload: rep.__payload,
+    statusCode: rep.statusCode
+  };
+
+  if (RESPONSE_BUFFER.length > 10) {
+    appendFileSync(
+      join(LOGS_DIRECTORY, RESPONSE_CAPTURE_FILE),
+      RESPONSE_BUFFER.map(rb => JSON.stringify(rb)).join('\n') + '\n'
+    );
+    RESPONSE_BUFFER = [savedReply];
+  } else {
+    RESPONSE_BUFFER.push(savedReply);
+  }
+}
+
+/**
+ * Returns a subset of the given object with the values or properties given removed.
+ * @param obj - An array or an object literal.
+ * @param vals - Items or properties to exclude from `obj`.
+ * @returns Subset of `obj`.
+ */
+function omit(obj: Record<string, unknown> | unknown[], ...vals: unknown[]) {
+  if (Array.isArray(obj)) {
+    return obj.filter(o => !vals.includes(o));
+  } else {
+    return Object.keys(obj)
+      .filter(k => {
+        return !vals.includes(k);
+      })
+      .reduce((acc, curr) => ({ ...acc, [curr]: obj[curr] }), {});
+  }
+}
+
+function include(obj: Record<string, unknown> | unknown[], ...vals: unknown[]) {
+  if (Array.isArray(obj)) {
+    return obj.filter(o => vals.includes(o));
+  } else {
+    return Object.keys(obj)
+      .filter(k => {
+        return vals.includes(k);
+      })
+      .reduce((acc, curr) => ({ ...acc, [curr]: obj[curr] }), {});
+  }
+}
+
+export default fp(shadowCapture);
diff --git a/api/src/utils/env.ts b/api/src/utils/env.ts
index 147a78e2e9d..c3abc0a1ea5 100644
--- a/api/src/utils/env.ts
+++ b/api/src/utils/env.ts
@@ -125,6 +125,8 @@ export const FCC_ENABLE_SWAGGER_UI =
   process.env.FCC_ENABLE_SWAGGER_UI === 'true';
 export const FCC_ENABLE_DEV_LOGIN_MODE =
   process.env.FCC_ENABLE_DEV_LOGIN_MODE === 'true';
+export const FCC_ENABLE_SHADOW_CAPTURE =
+  process.env.FCC_ENABLE_SHADOW_CAPTURE === 'true';
 export const SENTRY_DSN =
   process.env.SENTRY_DSN === 'dsn_from_sentry_dashboard'
     ? ''
diff --git a/sample.env b/sample.env
index 9574272d333..99d7d9cd59b 100644
--- a/sample.env
+++ b/sample.env
@@ -68,6 +68,7 @@ NODE_ENV=development
 PORT=3000
 FCC_ENABLE_SWAGGER_UI=true
 FCC_ENABLE_DEV_LOGIN_MODE=true
+FCC_ENABLE_SHADOW_CAPTURE=false
 
 # Email
 # use ses in production