diff --git a/cloudflare_ddns/app.py b/cloudflare_ddns/app.py
index 32af2ab..fc9d3cc 100644
--- a/cloudflare_ddns/app.py
+++ b/cloudflare_ddns/app.py
@@ -1,11 +1,11 @@
 import logging
 import threading
 from dataclasses import dataclass
-from typing import Tuple
+from typing import Tuple, List, Dict, NoReturn
 
 import requests
 
-from cloudflare_ddns.constants import VERIFY_TOKEN
+from cloudflare_ddns.constants import VERIFY_TOKEN, LIST_ZONES, LIST_DNS, ACCEPTED_RECORDS
 from cloudflare_ddns.utils import parse_duration, BearerAuth
 
 log = logging.getLogger("ddns")
@@ -15,21 +15,99 @@ log = logging.getLogger("ddns")
 class Domain:
     domain: str
     record_type: str
+    zone: str
+    id: str
 
 
 class ApplicationJob(threading.Thread):
-    def __init__(self, delay: str, token: str, raw_domains: Tuple[str], default_ipv6: bool):
+    def __init__(self, raw_delay: str, token: str, raw_domains: Tuple[str], default_ipv6: bool):
         super().__init__()
 
         self.stop_signal = threading.Event()
 
-        self.delay = delay
+        self.delay = None
+        self.domains: List[Domain] = []
+        self.found_domains: Dict[str, Domain] = {}
+
         self.auth = BearerAuth(token)
-        self.raw_domains = raw_domains
         self.default_ipv6 = default_ipv6
 
+        self.raw_domains = raw_domains
+        self.raw_delay = raw_delay
+
     def launch(self) -> None:
         self.validate_arguments()
+        log.debug("Starting job.")
+        self.start()
+
+    def run(self) -> None:
+        log.debug("Parsing domains.")
+        self.parse_domains()
+        log.debug(f"Using domains: {', '.join(f'{domain.record_type}:{domain.domain}' for domain in self.domains)}")
+
+        log.info("Starting app.")
+        self.update_records()
+        while not self.stop_signal.wait(self.delay):
+            self.update_records()
+
+    def update_records(self):
+        ...
+
+    def parse_domains(self):
+        type_1 = "A" if not self.default_ipv6 else "AAAA"
+        type_2 = "A" if self.default_ipv6 else "AAAA"
+
+        for zone_json in requests.get(LIST_ZONES, auth=self.auth).json()["result"]:
+            for record_json in requests.get(
+                    LIST_DNS.format(zone_identifier=zone_json["id"]),
+                    auth=self.auth
+            ).json()["result"]:
+                if record_json["type"] in ACCEPTED_RECORDS:
+                    domain = Domain(
+                        record_json["name"],
+                        record_json["type"],
+                        record_json["zone_id"],
+                        record_json["id"]
+                    )
+                    self.found_domains[f'{record_json["name"]}-{record_json["type"]}'] = domain
+
+        log.debug(
+            f"Found domains: "
+            f"{', '.join(f'{domain.record_type}:{domain.domain}' for domain in self.found_domains.values())}"
+        )
+        for domain in self.raw_domains:
+            if ':' in domain:
+                type_, domain = domain.split(':', maxsplit=1)
+
+                if type_ not in ACCEPTED_RECORDS:
+                    log.error(f"Invalid record type {type_}. Must be one of {', '.join(ACCEPTED_RECORDS)}.")
+                    log.info(f"Exiting with code 65.")
+                    exit(65)
+
+                if f"{domain}-{type_}" not in self.found_domains:
+                    log.error(
+                        f"Cannot find an {type_} record for the domain {domain} in your Cloudflare settings. "
+                        f"Have you defined this record yet?"
+                    )
+                    log.info(f"Exiting with code 65.")
+                    exit(65)
+            else:
+                if f"{domain}-{type_1}" in self.found_domains:
+                    type_ = type_1
+                elif f"{domain}-{type_2}" in self.found_domains:
+                    type_ = type_2
+                else:
+                    log.error(
+                        f"Cannot find the domain {domain} in your Cloudflare settings. "
+                        f"Have you defined this record yet?"
+                    )
+                    log.info(f"Exiting with code 65.")
+                    exit(65)
+
+            self.domains.append(self.found_domains[f"{domain}-{type_}"])
+
+
+
 
     def validate_arguments(self):
         failed = False
@@ -39,20 +117,21 @@ class ApplicationJob(threading.Thread):
             failed = True
 
         try:
-            self.delay = parse_duration(self.delay)
+            self.delay = parse_duration(self.raw_delay)
         except ValueError as e:
             log.error(f"Failed to parse delay: {e}")
             failed = True
 
-        try:
-            log.debug("Validating bearer token.")
+        if not failed:
+            try:
+                log.debug("Validating bearer token.")
 
-            self.validate_bearer()
-        except ValueError as e:
-            log.error(f"Failed to validate bearer token: {e}")
-            failed = True
-        else:
-            log.info("Successfully validated the bearer token.")
+                self.validate_bearer()
+            except ValueError as e:
+                log.error(f"Failed to validate bearer token: {e}")
+                failed = True
+            else:
+                log.info("Successfully validated the bearer token.")
 
         if failed:
             log.info("Exiting with code 64.")
diff --git a/cloudflare_ddns/constants.py b/cloudflare_ddns/constants.py
index 03d2fcd..cf2d5d0 100644
--- a/cloudflare_ddns/constants.py
+++ b/cloudflare_ddns/constants.py
@@ -5,3 +5,9 @@ DEFAULT_DELAY = "5 minutes"
 BASE_ENDPOINT = "https://api.cloudflare.com/client/v4/"
 
 VERIFY_TOKEN = BASE_ENDPOINT + "user/tokens/verify"
+
+LIST_ZONES = BASE_ENDPOINT + "zones"
+LIST_DNS = BASE_ENDPOINT + "zones/{zone_identifier}/dns_records"
+
+# Utilities
+ACCEPTED_RECORDS = ('A', 'AAAA')