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Database / 15 Sep 2026 / 5 min read

PostgreSQL Deferrable Unique Constraints Postpone Conflict Checks

A uniqueness rule can be valid for a transaction even when an intermediate statement temporarily creates duplicate keys. PostgreSQL supports that distinction through deferrable unique constraints: enforcement can move from each modifying statement to a later constraint-check point. This behavior changes transaction semantics rather than removing the rule. Duplicate values may exist transiently in transaction-local work, but a deferred constraint still has to be satisfied before the transaction can commit successfully.

PostgreSQL Database

Database / 15 Sep 2026 / 6 min read

PostgreSQL BRIN Unsummarized Ranges Expand Heap Rechecks

A PostgreSQL BRIN index can contain block ranges with no summary tuple. Newly completed ranges do not receive an initial summary merely because inserts crossed the range boundary. Until maintenance creates that summary, a BRIN scan cannot use range metadata to exclude the affected heap pages. This state is normal index maintenance behavior rather than index corruption. It follows from BRIN’s compact design: the index stores summaries for groups of adjacent heap pages instead of one entry per indexed row.

PostgreSQL Database

Database / 15 Sep 2026 / 3 min read

PostgreSQL BRIN Unsummarized Ranges Delay Page Skipping

A BRIN index does not maintain one index tuple for every heap row. It stores summary data for groups of adjacent heap pages. That compact structure also creates a maintenance boundary: a newly allocated block range can exist without a summary tuple, leaving the index without summary data for that range until a summarization event occurs. This state matters most on append-heavy tables. Existing summarized ranges continue to track inserted values, but a new range is not automatically given its initial summary under the default settings.

PostgreSQL Database

Database / 15 Sep 2026 / 5 min read

PostgreSQL B-Tree Skip Scan Repositions Index Searches

A multicolumn B-tree does not always require an equality condition on its first column to avoid reading the entire index. PostgreSQL can use skip scan to perform repeated targeted searches when a predicate constrains a later column and the planner estimates that repositioning will bypass enough index entries. Consider an index whose key order is (region, created_at): CREATE INDEX orders_region_created_at_idx ON orders (region, created_at); A query that filters only created_at has no explicit condition on region:

PostgreSQL Database

Database / 15 Sep 2026 / 6 min read

PostgreSQL B-Tree Fillfactor Reserves Space Before Page Splits

A PostgreSQL B-tree leaf page has finite space for index tuples. When an incoming tuple belongs on a page that no longer has room, the access method must make space, and a page split can add another leaf page plus a new parent downlink. The fillfactor storage parameter controls how tightly leaf pages are packed at selected points in the index lifecycle, leaving capacity that later writes can consume. For B-tree indexes, PostgreSQL uses a default fillfactor of 90. A value below 100 deliberately exchanges denser initial storage for free space on leaf pages. That space is not a permanent reservation for a particular row or key. It is simply unused page capacity available to later index activity.

PostgreSQL Database

Cybersecurity / 15 Sep 2026 / 6 min read

Permissions Policy Bounds Browser Feature Authority

Permissions Policy Bounds Browser Feature Authority A page can embed code from several origins while still presenting a single application surface. That composition becomes security-relevant when browser capabilities such as geolocation, camera access, microphone access, fullscreen, or payment functions are available inside the resulting document tree. The code that renders a widget may not need the same browser authority as the application that hosts it. Permissions Policy gives a site a way to restrict selected web-platform features by origin and frame. It is not a replacement for user permission prompts, sandboxing, application authorization, or browser isolation. Its value is narrower and architectural: it can remove capabilities from documents that have no legitimate reason to exercise them.

Cybersecurity Permissions Policy

Tech / 15 Sep 2026 / 6 min read

PCIe Link Width Sets How Many Lanes Carry Data

A PCI Express slot can look physically large while providing fewer active lanes than its connector suggests. A full-length slot may carry sixteen lanes, eight lanes, four lanes, or even one lane depending on the motherboard design and current resource allocation. PCIe calls these arrangements link widths. Common widths include x1, x4, x8, and x16. The number after the x indicates how many lanes participate in the link. That distinction matters for graphics cards, storage adapters, network cards, capture hardware, accelerators, and other devices that can move large amounts of data through an expansion slot.

PCI Express PCIe

Tech / 15 Sep 2026 / 5 min read

Path MTU Discovery Finds the Largest Packet a Route Can Carry

A host can know the maximum transmission unit of its own network interface without knowing the smallest limit farther along a route. Ethernet might accept one packet size while a tunnel, access link, or other intermediate network accepts less. Path MTU Discovery, commonly shortened to PMTUD, lets an endpoint adapt to that route-level limit. The mechanism matters because an IP packet that fits the sender’s local link can still be too large for a later hop.

Networking IP

Tech / 15 Sep 2026 / 5 min read

OLED PWM Dimming Turns Brightness into Timed Pulses

An OLED pixel does not need a backlight. Its organic emitters produce light directly, so panel electronics can regulate luminance at the pixel level. One common control method is pulse-width modulation, or PWM: emission alternates between active and inactive intervals, and the ratio of those intervals sets the average light output seen over time. That temporal pattern matters because a display can refresh an image at one rate while modulating emitted light at another. A 120 Hz refresh specification therefore says little by itself about the frequency or depth of brightness modulation.

OLED Displays

Cybersecurity / 15 Sep 2026 / 7 min read

OCSP Stapling Moves Certificate Status Into the TLS Handshake

OCSP Stapling Moves Certificate Status Into the TLS Handshake A valid certificate can become unsafe before its expiration date. A private key may be exposed, a certificate may be issued in error, or an operator may need to retire credentials early. Revocation exists for that gap, but checking revocation status creates another dependency on the path that is supposed to establish trust. The Online Certificate Status Protocol, or OCSP, gives relying parties a way to ask an issuer-designated responder about a certificate. A direct query can return a signed status response, yet it also adds network work outside the connection being authenticated. OCSP stapling changes the delivery path: the TLS server obtains the signed response and sends it to the client as part of the handshake.

Cybersecurity TLS

Tech / 15 Sep 2026 / 7 min read

NVMe Queues Let Storage Handle Many Commands in Parallel

NVMe storage does not send every read or write through one shared command line. The protocol is built around queue pairs: software places commands into a submission queue, and the controller reports finished work through a corresponding completion queue. That structure matters most when several processor cores and application threads are generating storage work at the same time. Multiple queues can distribute command handling across cores, reduce contention around a single software path, and keep a fast solid-state drive supplied with enough outstanding work.

Storage NVMe

Cybersecurity / 15 Sep 2026 / 7 min read

NSEC3 Trades DNSSEC Name Exposure for Operational Cost

NSEC3 Trades DNSSEC Name Exposure for Operational Cost A signed DNS zone has to authenticate absence as well as presence. When a resolver asks for a name that does not exist, a DNSSEC-validating resolver needs cryptographic evidence that the negative answer was not forged by an intermediary. The original NSEC mechanism supplies that evidence by linking existing names in canonical order. That design has a side effect: the links expose names. Following NSEC records can reveal much of a zone even when ordinary DNS queries do not provide an enumeration interface.

Cybersecurity DNSSEC

Cybersecurity / 15 Sep 2026 / 8 min read

Mutual TLS Moves Service Identity Into the Handshake

A service accepts HTTPS only from a small set of internal workloads. Server-side TLS protects the channel and authenticates the server, but any client able to reach the listener can still start a connection. An API token can authenticate the caller after the TLS session exists, yet that design places client identity above the transport boundary and creates another bearer credential to distribute. Mutual TLS, commonly shortened to mTLS, changes that boundary. The server requests a client certificate during the TLS handshake, validates the presented certificate according to its configured trust policy, and requires cryptographic proof that the peer controls the corresponding private key. The resulting connection can carry an authenticated client identity before application data is accepted.

Cybersecurity TLS

Cybersecurity / 15 Sep 2026 / 7 min read

Mutual TLS Moves Client Identity Into the Handshake

Mutual TLS Moves Client Identity Into the Handshake An internal API can receive a perfectly encrypted TLS connection and still have no cryptographic evidence about the process at the other end. Ordinary server-authenticated TLS proves the server’s identity to the client and protects traffic in transit, but the application still needs another mechanism to identify its caller. Mutual TLS, commonly shortened to mTLS, adds certificate-based client authentication to that exchange. The server requests a client certificate, validates the presented chain according to its trust policy, and verifies a signature proving possession of the corresponding private key. The result is a transport connection associated with a cryptographic client identity before ordinary application requests are processed.

Cybersecurity Mutual TLS

Artificial Intelligence / 15 Sep 2026 / 6 min read

Measure Anisotropy in Embedding Spaces

Embedding vectors can occupy a narrow cone instead of spreading evenly across their available dimensions. In that geometry, unrelated items may still have noticeably positive cosine similarity because many vectors share a common directional component. This concentration is called anisotropy. For developers, anisotropy matters at the point where vector geometry becomes an application signal. A similarity threshold, nearest-neighbor ranking, clustering rule, or novelty detector inherits the distribution produced by the embedding model. The same cosine value can carry different meaning across representation spaces with different directional concentration.

Artificial Intelligence Embeddings

Cybersecurity / 15 Sep 2026 / 8 min read

JWKS Rotation Makes Cache Lifetime Part of Token Verification

A service receives a valid JWT seconds after its issuer rotates signing keys. The token carries a new kid, but the verifier still has the previous JWK Set in cache. Signature verification cannot even begin with the correct public key until the verifier obtains a set containing that identifier. This is a routine rollover condition, not a cryptographic break. Yet it exposes an important boundary in distributed token validation: a verifier that obtains public keys remotely depends on cache behavior and key publication timing alongside the signature algorithm itself.

Cybersecurity JWT

Artificial Intelligence / 15 Sep 2026 / 5 min read

Isolate Attention Across Packed Training Sequences

Padding can consume a large share of a training batch when sequence lengths vary. Sequence packing reduces that waste by placing multiple short samples into one token block. The arithmetic is attractive: more non-padding tokens fit into the same fixed-length tensor. Packing also changes the structure seen by attention. A standard causal mask only prevents a token from attending to later positions. It does not know that two adjacent spans came from separate samples. Without an additional boundary constraint, a token in the second span can attend to tokens from the first span.

Artificial Intelligence Transformers

Software Engineering / 15 Sep 2026 / 7 min read

Idempotency Keys Bind Retries to One Logical Operation

A client can transmit a state-changing request, lose the response, and retry without knowing whether the first attempt committed. At that boundary, transport failure has created ambiguity rather than proof of application failure. Repeating the mutation blindly can create a second logical effect. An idempotency key gives the server a stable operation identity across those delivery attempts. The first accepted request associates the key with an operation record. A later request carrying the same key can then reuse the recorded outcome instead of executing the mutation again.

Software Engineering APIs

Cybersecurity / 15 Sep 2026 / 7 min read

HTTP Request Smuggling Starts at Message-Boundary Disagreement

HTTP Request Smuggling Starts at Message-Boundary Disagreement A reverse proxy can validate an HTTP request, forward it to an application server, and still leave both systems with different views of where that request ends. The bytes do not need to change in transit. The security failure appears when two parsers assign different boundaries to the same stream. That disagreement is the core of HTTP request smuggling. One component consumes a prefix as a complete request while another treats additional bytes as part of that request, or as the beginning of a following one. On a reused backend connection, the leftover bytes can alter the interpretation of traffic that arrives later.

Cybersecurity HTTP

Software Engineering / 15 Sep 2026 / 8 min read

HTTP Preconditions Turn Resource Versions Into Write Guards

A client reads a resource at revision 41, edits one field, and sends the whole representation back. During that interval, another client commits revision 42. If the server accepts the first client’s replacement without testing its source revision, revision 42 can disappear from the visible state even though both requests completed normally. This is the lost-update shape at an HTTP boundary. The notable detail is not simultaneous execution. The requests can arrive seconds apart. The conflict exists because a later mutation was derived from an earlier representation and the server has no condition connecting those two facts.

Software Engineering HTTP

Cybersecurity / 15 Sep 2026 / 6 min read

HSTS Turns HTTPS Preference Into Browser Policy

HSTS Turns HTTPS Preference Into Browser Policy An HTTPS site can configure perfect TLS and still expose a weaker first contact. If a person types a bare hostname, follows an old http:// bookmark, or opens an insecure link, the browser may send an HTTP request before the server redirects it to HTTPS. An active network attacker gets an opportunity before the protected connection exists. HTTP Strict Transport Security, or HSTS, moves that redirect decision into the browser. After a browser receives a valid HSTS policy over HTTPS, it records that the host must be contacted securely for the policy lifetime. Later HTTP navigation to that host is upgraded locally rather than sent across the network as cleartext HTTP.

Cybersecurity HSTS

Cybersecurity / 15 Sep 2026 / 6 min read

HSTS Turns First Contact Into Persistent HTTPS Policy

A site can redirect every plain HTTP request to HTTPS and still expose a gap before that redirect arrives. On an untrusted network, the first cleartext request can be intercepted, altered, or answered by another system before the browser receives the server’s redirect. TLS cannot protect a request that has not entered TLS yet. HTTP Strict Transport Security changes browser behavior after a secure contact. A conforming user agent that receives a valid Strict-Transport-Security field over HTTPS records a policy for the host. During the policy lifetime, later attempts to use HTTP for that host are rewritten to HTTPS internally before an insecure request is sent.

Cybersecurity Web Security

Tech / 15 Sep 2026 / 6 min read

Happy Eyeballs Races IPv6 and IPv4 Connections

A device on a dual-stack network can often reach the same service over both IPv6 and IPv4. DNS may return AAAA records for IPv6 addresses and A records for IPv4 addresses, leaving the client with several possible routes to the destination. Preferring IPv6 and waiting for a complete failure before trying IPv4 sounds orderly, but it can create a visible pause when the IPv6 path is broken or unusually slow. The reverse ordering can hide IPv6 even when it offers a healthy path. Happy Eyeballs avoids both extremes by giving preferred connection attempts a short head start while allowing another address family to compete soon afterward.

Networking IPv6

Software Engineering / 15 Sep 2026 / 6 min read

Half-Open TCP Connections Hide Peer Failure Until Traffic Resumes

A TCP socket can remain in the established state on one host after the peer has become unreachable or has lost all connection state. No contradiction exists in that state: TCP endpoints maintain local protocol state, and a silent network failure does not automatically deliver evidence that the peer is gone. This creates a boundary between connection state and peer liveness. An established socket records what the local TCP implementation currently knows about a byte-stream association. It is not a continuously refreshed assertion that the remote process, host, route, and intervening network are all operational.

Software Engineering Networking