Adding or modifying a DNS record may seem like a simple console operation, but it's actually a precise adjustment to network traffic paths. Understanding and following key considerations can prevent service interruptions, security vulnerabilities, and performance bottlenecks, ensuring the smooth operation of digital services on the global network.

Before adding any DNS record, the first thing to do is thoroughly understand what you are doing and its scope of impact. DNS record types are diverse, each with a specific function: A records point a domain name to an IPv4 address, AAAA records correspond to IPv6, CNAME records create aliases pointing to another domain, MX records manage mail routing, and TXT records are often used for authentication and policy claims. Choosing the wrong record type is a common source of error—for example, setting `www.example.com` as a CNAME pointing to `example.com`, then attempting to add an MX record for `www.example.com` violates DNS protocol rules because CNAME records are mutually exclusive with other record types under the same domain.

Equally crucial is understanding the record's scope: Are you adding a record for the root domain (apex domain, such as `example.com`) or a subdomain (such as `blog.example.com`)? Operations involving root domains require extreme caution, as they impact all services under the entire domain and are subject to certain technical constraints (e.g., root domains typically cannot be set as CNAME records unless special alias records provided by the DNS provider, such as ALIAS or ANAME, are used).

In practical implementation, every parameter setting requires careful consideration. TTL (Time-To-Live) is the most easily underestimated yet crucial parameter, determining the lifespan of DNS records across various levels of caching servers. A shorter TTL (e.g., 300 seconds) means changes take effect quickly globally, facilitating failover and A/B testing, but also increases the query load on authoritative DNS servers. A longer TTL (e.g., 86400 seconds) reduces server load and improves query speed, but global cache refresh becomes exceptionally slow when changes are needed. A wise approach is to initially lower the TTL value before making changes, and then gradually increase it to normal levels after the changes are complete and stable. For load-balanced and high-availability architectures, multiple A/AAAA record values ​​must be configured for the same host record, providing basic client round-robin load balancing and redundancy. However, ensure that these IP addresses actually correspond to servers providing normal services. The DNS layer is only responsible for returning address lists and does not verify the health status of backend services. True health checks should be performed at the application layer or using more advanced DNS services (such as GSLB which supports health checks).

Security and protection considerations should be integrated throughout DNS configuration. The primary principle is to implement least privilege management, strictly restricting access to and modification of the DNS console, and enabling operation log auditing. Be wary of DNS hijacking and cache poisoning attacks, and ensure the use of a trusted DNS service provider, which typically offers DNSSEC (DNS Security Extensions) services. Enabling DNSSEC for critical domains provides digital signature verification for DNS responses, effectively preventing man-in-the-middle tampering with resolution results. Another key point is to handle internal service records with care: never expose server IP addresses accessible only to the internal network through public DNS records; this is tantamount to revealing the internal network blueprint to the public. Internal services should be managed using completely independent internal DNS domains or split-view DNS.

Change management processes become particularly important when modifying DNS records involving existing services. Any change to the domain names pointing to the production environment must be considered a high-risk operation. Develop a detailed rollback plan and record the exact values ​​and TTLs of all relevant records. Testing changes beforehand in an incognito browser window or using command-line tools like `dig` or `nlsookup` is good practice, but be aware that these tools may not immediately reflect changes due to local caching or DNS server differences. A structured verification process should include:

# Verify changes from different network locations and public DNS resolvers
dig @8.8.8.8 A example.com +short
dig @1.1.1.1 A example.com +short
# Check global effectiveness (simple simulation)
for resolver in 8.8.8.8 1.1.1.1 208.67.222.222; d
echo "Query resolver $resolver:"
dig @$resolver A example.com +short

For services serving global users, geo-intelligent resolution should also be considered. If your service has servers deployed in different regions, you should use a geolocation-enabled DNS service to return the optimal IP address based on the user's origin. The coverage definition for each region must be clearly defined during configuration to avoid overlaps or omissions.

Long-term maintenance of DNS records requires a clear documentation and monitoring system. Maintain a "map" of all critical domain names, recording their purpose, target IP, responsible team, and expiration date. Especially for domains used in SSL/TLS certificates, any unintentional record modification can lead to certificate verification failure. Set up monitoring alerts for critical DNS records to monitor whether their resolution results suddenly become unknown IPs, whether they cannot be resolved, or whether the TTL value has been unexpectedly changed. Regularly audit all DNS records, cleaning up old, orphaned records pointing to offline services or test environments. These records are called "DNS zombie records," which not only increase management complexity but can also be exploited by attackers for subdomain takeover attacks.

Ultimately, adding DNS resolution records connects abstract domain names to physical servers, guiding global traffic flow. It requires operators to possess the rigor of a network engineer, the vigilance of a security expert, and the foresight of an architect. Every click to "Confirm Add" should be a comprehensive confirmation of the record type, value, TTL, security, global impact, and change process. In the era of cloud-native and microservices, the role of DNS is becoming increasingly critical, and dynamic configuration is becoming more frequent, but the core principles remain unchanged: clear understanding, pre-planning, cautious operation, and continuous verification. Only in this way can we ensure that every adjustment to this fundamental internet service layer becomes a reliable cornerstone supporting the steady progress of business, rather than the prelude to an unexpected service interruption.