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The DNS resolver decides how quickly the first network step starts, because it translates domains into IPs and thus the Loading time of the page even before the first byte. I shorten this step measurably if the DNS resolver is close to the user, caches efficiently and answers queries without detours.
Key points
I have summarized the following key messages so that you can understand the most important Lever recognize immediately.
- cache hit reduce the DNS time from tens of milliseconds to almost zero.
- Recursive DNS is slower the first time it is called up, then lightning fast.
- TTLs control queries, latency and update behavior.
- Anycast brings the resolver closer to the user.
- DoH/DoT protects requests without loss of speed.
Why DNS resolvers have a noticeable impact on loading time
Each page request starts with a DNS lookup, and this is where I decide on speed or waiting time. A fast resolver answers known targets directly from the Cache; This saves round trips to root, TLD and authoritative servers. Cold caches need more hops and noticeably increase the time until the first connection. I compensate for this by using resolvers with a high cache quota, short internal latency and clever prefetching. This shortens the path to the IP before TCP, TLS and the actual data transfer even start.
This is how the resolution works: From the cache to the authoritative
Is there a local Cache the resolver queries recursively: first root, then TLD, and finally the authoritative servers of the target domain. Each hop costs time, especially if the node is far away or overloaded. I reduce the hops by using resolvers with good peering and Anycast-proximity. After that, responses end up in the cache again, which dramatically speeds up the next call. The higher the cache hit rate, the less often the resolver has to query the open Internet at all.
Cache strategies that really work
I raise the Cache hit rate, by expanding the cache size of the resolver and keeping negative responses (NXDOMAIN/NODATA) meaningful. I only set short TTLs around moves or releases, otherwise they waste queries and time. For external resources, I use DNS prefetch so that the browser resolves the most important destinations before they are used. With a lot of recurring traffic, a recursive resolver pays off, because subsequent resolutions are almost completely free. Latency take place. I provide a practical overview with in-depth tips in the guide to DNS caching.
Recommended TTLs by record type
The choice of TTL controls load, timeliness and speed; I adapt it to change frequency and risk. High values protect the network and provide constant response times, low values accelerate switchovers but cost queries. For upcoming migrations, I lower the TTL days in advance, carry out the change and then increase it again. In this way, I ensure fast resolution on a day-to-day basis and keep the Control. The following table shows sensible guide values together with typical risks and information.
| Record type | Recommended TTL | Application | Risk | Note |
|---|---|---|---|---|
| A / AAAA | 1-24 h (migration: 5-15 min) | Web server IP | Delayed switching | Lower before moving, raise afterwards |
| CNAME | 30 min - 4 h | CDN or service assignment | Cascade lookups | Keep chains short |
| MX | 4-24 h | E-mail routing | Misrouting with changes | Change rarely, test thoroughly |
| TXT | 1-12 h | SPF, DKIM, Ownership | Incorrect authentication | Plan rollout, check impact |
| NS | 24-48 h | delegation | Resolution error | Only selectively adapt |
| SRV | 1-12 h | Service endpoints | Unreachability | Use health checks |
For CDNs and multi-region setups, I keep chains short so that the Response time does not grow with every jump. Where IP changes are rare, I save resources by using long TTLs. For aggressive deployments, I plan switching windows in advance. I then increase the TTL back to a reasonable level so that the Latency does not suffer.
Reduce global latency: anycast, geo and routing
With Anycast I can reach the nearest resolver node, which reduces ping times and cushions outages better. Good providers announce the same IP worldwide and automatically direct me to the next instance. Geo-DNS also distributes users to nearby destinations, which has a positive impact on TTFB and bandwidth requirements. To ensure that this runs smoothly, I pay attention to good peering and route optimization of the DNS provider. A well-founded introduction is provided by the clear page on DNS architecture, which explains the connections in a condensed form.
Browser and system caches: what really happens on the client
In addition to the network resolver, the Browser and OS caches the Loading time. Operating systems use a stub resolver that holds responses for seconds to minutes; browsers also maintain their own host caches with parallel name resolution. I make sure that these layers don't work against me: excessive search domains and high ndots-values produce unnecessary suffix lookups and cost time. In container and VDI environments, I often reduce ndots to 1-2 so that queries are sent directly as FQDNs.
Because browsers cache negative responses for a short time, I always diagnose changes by deliberately emptying the cache: flush the OS cache, restart the browser and check the resolver cache statistics if necessary. This is how I measure and evaluate real cold starts Warm starts realistic. For front ends I deliberately use dns-prefetch and preconnect, so that the browser resolves or initiates connections while idle without blocking the main path.
Dual stack, IPv6 and happy eyeballs
At dual stack-networks, it is not only the DNS time that is decisive, but also how the client deals with A and AAAA responses. I ensure clean IPv6 accessibility so that Happy Eyeballs does not fall back to IPv4 due to broken AAAA paths and waste seconds. A fast resolver delivers both records reliably, but the backend must serve v6 just as stably as v4. On the resolver side, I avoid artificial delays between A/AAAA and ensure fast parallel resolution.
In pure IPv6 setups with DNS64/NAT64 I plan additional lookup steps. Good resolvers cache synthesis results efficiently so that the overhead is not noticeable. I measure p95/p99 of the time until the first successful connection, because this is where a faltering v6 setup has the biggest impact.
ECS, geo-precision and data protection
CDNs optimize themselves through location proximity. EDNS Client Subnet (ECS) can customize responses to user regions, shortening the distance to the edge. I deliberately use ECS where third-party CDNs need it and deactivate or anonymize it when Privacy has priority. Short, regional prefixes often offer enough precision without giving away too much context. Important: I check how ECS affects the Cache hit rate so that the resolver cache is not split into too many segments.
Weigh resource hints correctly
dns-prefetch reduces the waiting time for reloaded domains, preconnect goes further and already sets up TCP/TLS (possibly QUIC). I only use preconnect for really critical destinations to avoid starting unnecessary connection fireworks. For large sites with many third-party domains, a small set of well-chosen hints brings significant Latency-advantages, while overuse clogs browser queues. In critical flows, a combination of preconnect for key destinations and dns-prefetch for „nice-to-have“ resources is often ideal.
Stale responses, aggressive NSEC and failure scenarios
For high Availability I work with „serve stale“: If an authoritative server fails for a short time, the resolver can pass on expired entries for a defined time and update them in the background. This avoids hard dropouts in the user path. I also use aggressive NSEC/NSEC3Caching to utilize negative answers for longer and save pointless follow-up questions. Together with prefetching for hot records, caches stay warm - even under varying loads.
Think authoritatively: delegation, glue and Apex-CNAME
On the authoritative side, I eliminate Delegation errorcorrect NS records, matching glue records and consistent TTLs across all nameservers. For CDNs at the zone apex, I set ALIAS/ANAME, to get CNAME-like flexibility without RFC breakage. I keep CNAME chains as short as possible and check whether third-party records create unnecessary detours. A clean authoritative configuration is the basis for the best resolver to fully exploit its potential.
Kubernetes, microservices and internal resolution
In cluster environments with high QPS, I pay attention to CoreDNS-scaling, sufficient cache and meaningful search-suffices. The ndots default value, which is often too high, leads to many internal suffix lookups before an FQDN goes to the Internet. I lower ndots and define only necessary search paths so that external targets are resolved without delay. For service discovery, I plan TTLs so that rolling updates are quickly visible but not jittery.
Resolver selection: Criteria and measurement methods
I check the Response times of the resolver from several networks, at different times of the day and week. I measure cold start (without cache) and warm start (with cache) to see real effects. I also monitor error rates, timeouts and the size of the EDNS buffer to ensure that responses do not fragment. For browser paths, I test how quickly third-party domains are resolved, as they often use the Critical path extend. If you measure regularly, you can detect fluctuations early on and make targeted adjustments to providers or settings.
Security and data protection without loss of speed
I secure DNS with DNSSEC, to prevent tampering, and true privacy with QNAME minimization. Rate limiting protects resolvers from amplification attacks and reduces the error rate under load. For encrypted transport paths, I use DoT or DoH without noticeably increasing latency. Modern implementations keep sessions active and avoid unnecessary handshakes. Practical tips on DNS over HTTPS help me to find security and Performance to connect cleanly.
Configuration: settings that save time
I scale the Cache size of the resolver so that frequently used zones are always in memory. Minimal responses reduce packet sizes, which increases the success rate via UDP. A sensible EDNS buffer size prevents fragmentation without creating path MTU problems. I shorten the jumps in CNAME chains so that the lookup does not scan several destinations. I also use prefetch logic for popular entries so that warm Caches are the rule.
Typical stumbling blocks and direct remedies
High first DNS times often indicate a lack of Cache or poor peering; then another resolver or recursion with large cache capacity helps. Inconsistent TTLs across name servers lead to contradictory responses and slow rollouts. TTLs that are too short flood resolvers with requests and push up latency. Misconfigured DNSSEC chains generate SERVFAILs, which slows down the user path. I systematically go through these points until metrics and Experience match.
Measurement practice: cold, warm, realistic
I measure reproducibly: first Cold start (clear cache, then dissolve), then Warm start (immediate repetition) and finally Realistic use (mixed sequences with other queries). I note p50/p95/p99, packet loss, RCODEs and the distribution of A/AAAA. I also observe whether EDNS responses fragment; if this occurs, I reduce the buffer size and activate TCP/DoT/DoH fallbacks. It is important for me to measure third-party domains in the overall context because they influence the Critical path often dominate.
Practical example: From 180 ms DNS to 20 ms
One project started with a slow Resolution, because the forwarder I was using was far away and did not offer any caching. I migrated to a recursive resolver with anycast proximity, increased the cache and activated prefetching. At the same time, I shortened CNAME chains and used EDNS sensibly to avoid fragmentation. The resulting DNS time dropped to a median of 20-30 ms, warm starts were sometimes less than a millisecond. This significantly improved the first byte time, and the Conversion attracted.
Summary: What I pay attention to for fast page load times
I choose one Anycast-The result is a resolver with a high cache share, sensible TTLs and clean peering. Recursive resolution pays off because subsequent resolutions take place with virtually no waiting time. Consistently set TTLs, short CNAME chains and minimal responses save additional milliseconds. I implement security via DNSSEC, QNAME minimization and DoH/DoT without any noticeable loss of speed. If you combine these levers and measure them regularly, you can keep the DNS time in the single-digit to low double-digit millisecond range and measurably accelerates each subsequent charging phase.
