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Make each door’s authorization decision locally: the controller should check a verified local policy, evaluate the credential and schedule, and actuate the relay without waiting for a cloud response. Treat that policy as a versioned snapshot, define what happens when it gets stale, and keep synchronization and audit replay from competing with live access decisions. An offline controller cannot receive a central revocation; that security window must be an explicit part of the design.
What should happen when the network goes down?
A door can continue operating offline only with the authorization information already available at the reader or controller, or carried through an offline credential method. A centrally added permission cannot take effect at an isolated door until the update reaches it. The same limitation applies to revocations: while disconnected, a controller may continue accepting a credential that was revoked centrally.
Keep the credential decision and relay command on the local path. Cloud services can distribute policy, collect events, and report device status, but a cloud round trip should not be a prerequisite for a routine entry decision. This is an architectural recommendation, not a latency guarantee: the cited product and project documentation does not establish a universal reader-to-relay response time.
Choose where authorization lives
Offline behavior depends on whether the authorization data is held at the reader, at the door controller, or in an offline credential path. Those arrangements are not interchangeable. A reader cache may contain only recently used credentials, while a controller may run its last received configuration. Ask how the initial policy is populated, what it contains, how often it refreshes, and whether the reader can still reach the controller locally during a WAN outage.
#1 Best Overall
- Access control keypad is sturdy rugged keypad; with zinc alloy electroplated technology;The circuit board is completely encapsulated in epoxy to be weatherproof; keyboard is waterproof so you can use it outdoor or indoor
- Key backlight function; the keys light will stay on in dark places or at night; indicator light; Red light stands for enter into programming mode; Yellow light for in the programming mode;Green light for operation successful mode
- Wiegand access control keypad can be as a standalone reader or keypad;0-99s adjustable door relay time; It is a relay output to open the door; so that you could connect this to a powered device without the use of some computing intermediate
- Easy to use;full programming from the keypad;support 3 access ways for card;PIN or card with PIN;you can set the public password or private password and the password can be changed which is more secure and personalized
- You can use the access control keypad to add and delete 2000 user information; set the door open delay time; it is suitable for garages; shops; homes; warehouses; laboratories; it has short circuit protection
Kisi documents reader-cache, controller-cache, and offline phone-credential fallback mechanisms. Its reader cache is populated from recent credential use; the documentation says it can cover outages for up to 36 hours, hold up to 1,000 access rights and 250 groups in less than 0.2 MB, and synchronize changed credentials within minutes. The same documentation says the API synchronizes with the reader cache once daily at midnight. These are Kisi-specific descriptions, not general guarantees, and the daily sync detail means a newly added credential may not be available through that offline reader path immediately.
Verkada describes controllers continuing with the last configuration received before an outage and storing events locally for later upload. Its example says a badge added in the cloud while a controller is offline will not work until connectivity returns and the controller receives the new configuration; the example says the update arrives within seconds. That timing describes the scenario, not a guaranteed convergence service level.
How should local policy be cached and invalidated?
Do not treat cache invalidation as a message that is guaranteed to reach every door. During a partition, a disconnected controller cannot learn about a change. Instead, make policy freshness observable and define how much stale authorization the deployment will tolerate.
Rank #2
- Material: Use high quality metal material, wear resistance, high temperature resistance, with surface protection. Durable for using
- Features: With digital button, full programming from the keypad. Such as add/delete cards, set password. With door bell button and blue backlight
- Functions: Three open door modes: Card, password, Card + password. 1000 user capacity
- Accessories: Equipped with a rainproof & waterproof cover. You can use it out of the door. Package also including 10 pieces blue RFID keyfobs
- Applications: Suitable for home, hotel, office, apartment, factory, and other commercial or residential entry systems
Use complete, authenticated policy versions
- Build a complete candidate snapshot. Include the access rights, schedules, and other decision inputs required by the controller, and identify the policy version and creation time.
- Authenticate and validate before use. Verify the signature and integrity of the downloaded snapshot, then check that it is complete and compatible with the controller.
- Activate atomically. Switch from the old policy to the new one only after validation succeeds. A partial transfer should not leave the controller evaluating a mixture of old and new permissions.
- Report active state. Expose the active version, last successful update time, and sync status so operators can distinguish a current controller from one running stale policy.
OpenLatch documents an implementation example in which an ESP32 makes local decisions from a cryptographically signed allow-list cached in local flash and periodically syncs that list from a backend. This illustrates signed local policy; it is a project design example, not an independent performance comparison. Versioning, atomic activation, and status reporting are recommendations for the design, not claims about every commercial platform.
Set an explicit stale-policy rule
Choose the response to prolonged disconnection by door and risk level. Possible policies include continuing to use the last verified snapshot for a defined period, denying selected high-risk access when policy age exceeds a threshold, or requiring a fresh check for narrowly selected actions when connectivity exists. The appropriate rule depends on the facility’s safety and security requirements; there is no universal offline expiry period established by the cited sources.
Record the policy age and make the threshold actionable. For example, define who is alerted when a controller exceeds the permitted age, what local behavior follows, and how staff handle a legitimate user whose new permission has not reached an isolated door. Avoid implying that a central revocation is effective at a disconnected controller.
Rank #3
- 12-button, always-on backlit keypad with stainless-steel face
- Supports 1,000 permanent codes, 50 guest codes (4-8 digits)
- Auto-disable access at specific times with built-in clock
- Egress input allows exit without code entry
- Auto-adjusting operation - 12-24 VDC/VAC
How can relay latency stay predictable?
Measure the full physical path, not just a network request or an application function: start at credential presentation and stop at the electrical relay transition. Credential decoding, local authorization lookup, schedule evaluation, and relay actuation all contribute to the result.
- Keep the decision path local and bounded; do not wait for cloud authorization during normal offline-capable operation.
- Prevent background sync and audit upload from holding locks or exhausting storage, CPU, or other resources needed for decisions.
- Keep device-event and policy-update handling from blocking the relay command.
- Measure on the selected reader, controller, wiring, and relay hardware under normal and degraded operating conditions.
The DEV post that frames this scenario describes embedded Linux controllers, biometric terminals, encrypted RFID readers, OSDP v2.2 over RS-485, local relay actuation, and a sub-200 ms target. Those are the post author’s scenario assumptions, not verified deployment details or a published benchmark. Treat sub-200 ms as a target to test against the actual system, not as a result established by the available documentation.
What should happen when connectivity returns?
Reconnection is a consistency event, not simply a signal to start draining every backlog as fast as possible. The controller should apply a complete, authenticated newer policy and make its active version visible, while giving live access decisions priority over background recovery.
Rank #4
- ✅ 【Wireless Access Control System】Integrated wireless access control keypad allows you to control the keypad share, modify and delete passwords/ID cards, remote Unlock doors/gates, view access logs, manage users, and assign temporary or permanent access from your phone, anytime and anywhere
- ✅ 【Multiple Access Options】Come with 5PCS ID key fobs, support 2000 users capacity. Swipe card or password or TUYA APP multiple unlocking methods to open the door. Equipped with doorbell button, compatible with all electric locks.
- ✅ 【Reliable and Practical】The access control keypad with strong zinc alloy electroplated technology, epoxy to completely encapsulated, anti-prying hexagonal star screw, anti-vandal and weatherproof. Suitable for mounting either indoor or outdoor. Backlight design(non-turn-off), in dark locations or night you can read numbers.
- ✅ 【Widely Used】Wiegand access control keypad system can prevent unauthorized personnel from entering. Built in buzzer and light dependent resistor (LDR) for anti tamper. Can be as a standalone reader or keypad. Very suitable for garage, hotel, shops, warehouses, laboratories, other private spaces. Note: Models whose connection protocol is Wi-Fi, learn buttons, safety sensors, rolling code are not currently supported! Keypad uses 2-wire connection directly to the opener's push button switch terminals.
- ✅ 【Simple Setup for Use】Connect the access controller to the power supply and the electric lock, Keypad enter "*master code#73#" code, turn on wireless pairing, add the keypad to the TUYA APP, you can remotely manage the access control system. Attention: The password keypad working on 2.4 GHz network, when adding keypad, make sure the keypad must be connected to the same Wi-Fi network as your smartphone. Powered by 12V DC power supply (not included)
- Re-establish and authenticate the connection to the expected service.
- Receive the newest complete policy version and validate it before activation.
- Apply the version atomically, then report the active version and successful sync state.
- Resume buffered-event upload with sequence identifiers so duplicates and out-of-order delivery can be recognized and handled idempotently.
- Throttle replay or otherwise isolate its resource use so event upload cannot delay current credential checks or relay actuation.
These recovery steps follow from documented local caching and post-outage synchronization behaviors, but the exact protocol and ordering must be specified and validated for the chosen platform. Axis documentation describes a multi-controller consistency concern: configuration changes may depend on a connected majority, with an offline controller receiving updates after reconnecting. It also describes regular synchronization of device events and schedules. Such topology and synchronization rules matter when planning convergence; a network I/O relay module for remote functions such as elevator access is not evidence of improved door-response latency.
How should buffered audit events be managed?
Local event storage preserves a record for later upload during an outage, but it introduces finite-capacity and recovery concerns. Verkada documents local event storage and later upload; the cited material does not specify a universal buffer size or replay scheduling guarantee.
- Persist each event with a sequence identifier and enough context to correlate it after upload.
- Monitor queue depth, storage consumption, and the age of the oldest unuploaded event.
- Define retention and alert behavior before the buffer reaches capacity, including what happens if storage fills.
- Prioritize live access decisions over replay and test the effect of a large backlog on controller resources.
What should you compare when selecting an implementation?
“Offline support” is not a single capability. Compare the behavior that matters to the door and to operations, and confirm platform-specific details with the vendor or project documentation.
Best Value
- 【Wide Compatibility】Wired keypad compatible with most brands of gate openers and garage door openers (whose control board accepts a “Dry Contact” signal or works with a wired Standard Wall Button or can be controlled by a momentary push button switch). ⚠️ Note: Models whose connection protocol is Wi-Fi, learn buttons, safety sensors, rolling code are not currently supported! It can also be used with magnetic lock, strike lock and access control systems for reliable keyless entry.
- 【Wired Access Control Keypad】The keypad uses contactless RFID and PIN code technology. Simply enter a short password or tap the keyfobs (5-incl.) to open the gate without carrying a key. Easy DIY installation and programming in minutes. Works with most garage door gate openers that accept dry contact input. ideal for homeowners, staff, visitors, or delivery access needs.
- 【Safe to Use】Support up to 2000 standard users. 3-working modes “Code”, “ID Card”, “Code + ID card”, Provide more convenience for family or trusted friends. The ID card type is 125KHz EM or ID card / tag (incl. 5-keyfobs). User data is stored locally on the keypad for secure offline control—no extra software or internet required.
- 【Ideal for Outdoor Use】Coming with zinc alloy housing and LED backlight metal buttons, internal epoxy to potting, IP68 weaterproof, allowed to work outdoors long-term use in rain and sunlight. Connect the keypad's blue and purple wires to the garage door/gate opener's wall push button switch, and the red and black wires directly to the 12V DC power(not included). operates on 12V DC power and is ideal for both residential and commercial automatic gate systems.
- 【Multiple Applications】This keyless entry device is designed for the household, courtyard, warehouse, school, office building and other commercial sites. Suitable to operate the magnetic lock (normally close signal) or electric strike door lock (normally open signal). Standard Wiegand 26 output, work as an extra card reader.
| Design axis | Questions to resolve |
|---|---|
| Authorization location | Is policy held by the reader, the door controller, or an offline credential path? Can the reader still communicate with the controller locally without WAN access? |
| Cache population and refresh | Does the cache contain the full policy or credentials seen recently? How is the initial cache populated, and what are the documented refresh paths and cadences? |
| Revocation window | What remains authorized during a partition, how is policy age tracked, and what action follows when the allowed staleness threshold is exceeded? |
| Recovery behavior | Are updates complete and authenticated, can they be activated atomically, and can operators see which version is active after reconnect? |
| Topology and consistency | What local network path is required between reader and controller? Do multi-controller changes require connectivity among a group of controllers? |
| Event handling | How much event data can be buffered, what happens at capacity, and can replay be throttled to protect live decisions? |
| Physical response | What is the measured credential-to-relay time on the actual hardware during WAN loss, backlog replay, reconnect, peak use, and reboot? |
Kisi documents local reader-to-controller communication over UDP port 62435 and says local connectivity is needed for offline support. Its Controller Pro 1 product page describes four dry or wet relay outputs. Those are product-specific network and output details; they do not establish a general relay-latency result.
How should the design be tested?
Test the complete door path and record both the physical response and the controller’s policy and sync state. A passing result should show that the relay behavior remains within the deployment’s target while the controller is offline or doing recovery work.
- Disconnect WAN access while preserving or intentionally disrupting the local reader-controller path, then verify the expected offline behavior for already cached and unavailable credentials.
- During the outage, change permissions centrally and confirm that the isolated door behaves according to the documented stale-policy rule.
- Reconnect while policy reconciliation and event replay are active; measure credential-presentation-to-relay-transition time and verify the active policy version.
- Repeat with the event queue near its planned capacity, under peak credential throughput, and during controller reboot.
- Verify event sequence handling, duplicate tolerance, storage alerts, and the defined behavior if the buffer fills.
Record hardware, firmware, network conditions, test load, and measurement method alongside results. That makes a latency target meaningful for the actual installation rather than an unsupported assumption about all controllers.
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