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Database / 14 Sep 2026 / 4 min read

PostgreSQL Expression Indexes Store Derived Keys

A PostgreSQL index key does not have to be a column copied directly from a table row. It can be the result of an expression computed from that row. The stored key then represents the transformed value, allowing a matching predicate to use ordinary indexed access instead of computing the expression across every candidate row. Case-normalized text is a compact example. An application may preserve the original spelling of an email address while searching on a normalized form:

PostgreSQL Database

Database / 14 Sep 2026 / 5 min read

PostgreSQL Exclusion Constraints Block Overlapping Ranges

A unique constraint can reject two equal scalar values, but equality is too narrow for many scheduling and allocation rules. Two reservations can have different start and end timestamps while still occupying the same interval. PostgreSQL exclusion constraints express this kind of conflict directly in the database. An exclusion constraint compares pairs of rows with declared operators. A pair is rejected when every operator comparison in the constraint is true. This turns operators such as range overlap into enforceable cross-row rules without relying on a query followed by an insert.

PostgreSQL Database

Database / 14 Sep 2026 / 4 min read

PostgreSQL Deferrable Constraints Shift Check Timing

Most PostgreSQL constraints reject invalid state as soon as the relevant statement is checked. That timing is usually desirable, but some valid multi-statement changes pass through a temporary state that violates a uniqueness, foreign-key, primary-key, or exclusion rule. A deferrable constraint changes the timing rather than the rule itself. PostgreSQL can postpone its check until transaction commit, allowing intermediate row states that would fail under immediate checking. The final transaction state must still satisfy the constraint.

PostgreSQL Database

Database / 14 Sep 2026 / 6 min read

PostgreSQL CTE Materialization Controls Planner Boundaries

A PostgreSQL common table expression can either become part of the surrounding query plan or remain a separately computed result. That distinction changes more than plan shape. It controls whether restrictions can move across the CTE boundary and whether repeated references can cause repeated computation. Since PostgreSQL 12, a non-recursive, side-effect-free CTE is eligible for folding into its parent query. PostgreSQL normally folds such a CTE when the parent references it once. Multiple references normally lead to materialization instead. MATERIALIZED and NOT MATERIALIZED make that boundary explicit when the default does not fit the query.

PostgreSQL Database

Database / 14 Sep 2026 / 5 min read

PostgreSQL BRIN Indexes Summarize Block Ranges

A PostgreSQL BRIN index does not store one index entry for every indexed row. It stores summary data for consecutive ranges of heap blocks. That distinction gives BRIN a very different cost and selectivity profile from a B-tree. The access method fits large tables where indexed values tend to follow heap location. Timestamped append-heavy data is a common shape: older values tend to occupy earlier blocks and newer values tend to occupy later blocks. A range predicate can then eliminate many block ranges using compact summary data.

PostgreSQL Database

Database / 14 Sep 2026 / 5 min read

PostgreSQL Bitmap Scans Combine Index Results

A PostgreSQL query does not need a single index that represents every useful predicate. The planner can scan separate indexes, turn their matching tuple locations into bitmaps, combine those bitmaps, and then visit the required heap pages. This is the basis of bitmap index scans and Bitmap Heap Scan plans. The mechanism sits between two familiar choices. A sequential scan reads the table broadly, while a plain index scan follows index entries to heap tuples as it encounters them. A bitmap plan first gathers locations, then performs heap access as a distinct phase.

PostgreSQL Database

Database / 14 Sep 2026 / 5 min read

PostgreSQL B-Tree Deduplication Packs Duplicate Keys

A PostgreSQL B-tree can represent several equal index keys with one physical key value followed by multiple heap tuple identifiers. This representation, called a posting-list tuple, reduces repeated key storage on leaf pages without changing the logical contents of the index. The mechanism matters most when an indexed value occurs many times. An index on a low-cardinality status column, for example, may contain thousands of entries whose key is pending. Logically those entries still identify separate table tuples. Physically, B-tree deduplication can pack groups of equal keys so the key datum is stored once for a group of TIDs.

PostgreSQL Database

Software Engineering / 14 Sep 2026 / 7 min read

Poison Messages Turn Retries Into Queue Retention

A queue consumer receives a message, rejects it, and receives the same message again. That cycle is useful when the rejection came from a transient condition. It is structurally different when the payload can never be processed by the current consumer. The broker can keep honoring redelivery semantics while the application makes no forward progress on that message. Such a message is commonly called a poison message. The important property is not that it contains malformed bytes. A syntactically valid message can be permanently unprocessable because its schema is unsupported, a required invariant is violated, referenced data can never exist, or application logic deterministically rejects its state.

Software Engineering Distributed Systems

Cybersecurity / 14 Sep 2026 / 7 min read

PKCE Binds an OAuth Code to the Client That Started the Flow

An OAuth authorization code can pass through a browser, an operating-system URL dispatcher, a custom application scheme, or an application link before it reaches the client that requested it. That route is convenient, but it also means possession of the returned code is not always strong evidence that the intended client received it. Proof Key for Code Exchange, usually called PKCE, changes the value of an intercepted code. Before starting the authorization request, the client creates a high-entropy secret called the code verifier. The authorization server receives a derived code challenge with the request and later requires the original verifier when the code is exchanged for tokens. A party that captures only the authorization code lacks the second value needed to complete the exchange.

Cybersecurity OAuth

Tech / 14 Sep 2026 / 6 min read

Passkeys Bind Sign-In Credentials to Site Domains

Passwords are portable by design. A person can type the same secret into a legitimate service, a lookalike page, or an unrelated application. That flexibility is convenient, but it also gives phishing pages a chance to collect credentials that can later be replayed against the real service. Passkeys change the shape of sign-in. Instead of sending a reusable secret to a server, a device proves possession of a private key. The matching public key is stored by the service, while the private key remains under control of the user’s authenticator or credential provider.

Tech Passkeys

Cybersecurity / 14 Sep 2026 / 8 min read

Outbound Requests Turn Application Features Into Network Authority

A URL field can look like ordinary application input until the server acts on it. Image importers, webhook testers, document renderers, link previews, feed readers, and integration checks all have legitimate reasons to make outbound requests. The security boundary changes at the moment untrusted input influences the destination: the application is no longer processing a string; it is lending its own network position to a caller. Server-side request forgery, commonly abbreviated SSRF, emerges from that mismatch in authority. An external caller may be unable to connect to an internal service, a loopback listener, or a cloud control endpoint directly. A vulnerable server can sometimes make that connection on the caller’s behalf. Authentication at the outer application does not erase the issue. The request originates from infrastructure that downstream systems may trust for entirely separate reasons.

Cybersecurity SSRF

Tech / 14 Sep 2026 / 7 min read

OLED PWM Dimming Controls Brightness With Light Pulses

Lowering a phone’s brightness slider does not always mean its OLED pixels simply emit a weaker, perfectly steady glow. Many OLED displays use pulse-width modulation, or PWM, for at least part of their brightness range. The pixels alternate between brighter and darker states quickly enough that the resulting light is perceived as a lower average level. This behavior is easy to miss during ordinary use because the modulation can happen hundreds or thousands of times per second. A camera with a suitable shutter setting may reveal bands, while measurement equipment can show the changing light output directly.

OLED Displays

Tech / 14 Sep 2026 / 8 min read

OLED Pixel Wear and Static Image Retention

OLED screens can produce deep blacks and strong contrast because each pixel generates its own light. A black pixel can simply remain off instead of relying on a shared backlight. That same self-emissive design also gives each light-producing element a finite operating life. As an OLED panel accumulates use, its subpixels gradually lose some ability to produce the same brightness from the same electrical drive. Normal aging is spread across the panel when content changes frequently. Static logos, status bars, game interfaces, navigation controls, or other fixed graphics can concentrate use in particular areas. If the difference becomes large enough, a faint trace of those shapes can remain visible during unrelated content.

Tech Displays

Cybersecurity / 14 Sep 2026 / 6 min read

OCSP Stapling Moves Revocation Evidence Closer to the TLS Handshake

OCSP Stapling Moves Revocation Evidence Closer to the TLS Handshake A browser can receive a valid certificate chain, verify every signature, confirm the hostname, and still face one more question: has the issuing certificate authority revoked the leaf certificate since it was issued? That question is awkward because the certificate itself cannot carry a fresh answer. Its signed validity interval is fixed at issuance, while revocation is an event that can happen later.

Cybersecurity TLS

Tech / 14 Sep 2026 / 4 min read

NVMe APST Moves Idle SSDs Into Lower Power States

An NVMe SSD can support several power states rather than operating at one fixed power level. Active states favor quick access and throughput, while deeper idle states can reduce energy use at the cost of extra time needed to return to full activity. Autonomous Power State Transition, commonly shortened to APST, lets the host configure automatic movement into selected lower-power states after defined idle periods. Once configured, the controller can perform those transitions without a separate host command for every idle event.

NVMe SSD

Artificial Intelligence / 14 Sep 2026 / 5 min read

Normalize Hidden States with RMSNorm

A hidden-state vector can grow or shrink in magnitude as it passes through a neural network. RMSNorm controls that scale by dividing the vector by its root mean square magnitude, then applying a trainable gain. Unlike LayerNorm, it does not subtract the vector mean before rescaling. That missing centering operation is the defining distinction. RMSNorm constrains scale while leaving a uniform shift across coordinates present in the normalized representation. RMSNorm uses the second raw moment For a hidden vector x with d coordinates, its root mean square is:

Artificial Intelligence Neural Networks

Tech / 14 Sep 2026 / 5 min read

NFC Phones Couple With Nearby Tags Through Magnetic Fields

Tapping a phone against a payment terminal, transit gate, or small sticker looks like a tiny version of ordinary wireless communication. The radio behavior is different from a Wi-Fi or cellular link, though. NFC is built for very short distances and commonly relies on magnetic coupling between antennas placed close together. That short operating range shapes both the hardware and the interaction. A phone can exchange data with another powered NFC device, but it can also communicate with a passive tag that has no battery of its own.

Tech NFC

Cybersecurity / 14 Sep 2026 / 6 min read

Mutual TLS Makes Client Identity Part of the Connection

A service can receive perfectly encrypted traffic from a client it should never have trusted. Ordinary server-authenticated TLS protects the channel and lets the client validate the server, but it does not automatically give the server a cryptographic identity for the caller. In machine-to-machine systems, that missing property is often filled by mutual TLS. Mutual TLS, commonly shortened to mTLS, extends the TLS handshake so that the server requests a certificate from the client. The client proves possession of the corresponding private key, and the server validates the presented certificate against an accepted trust policy. When that policy is tied to an application identity, the connection carries more than confidentiality and integrity: it also carries evidence about the peer that opened it.

Cybersecurity TLS

Tech / 14 Sep 2026 / 5 min read

Memory Compression Keeps More Active Data in RAM

Modern operating systems can hold compressed copies of memory pages in RAM when physical memory becomes crowded. The technique increases the amount of useful data that fits in a fixed quantity of RAM without changing the installed hardware. Compression is not free capacity. It exchanges processor time and some memory space for a smaller representation of data that would otherwise occupy more RAM or become a candidate for storage-backed paging.

Memory Operating Systems

Artificial Intelligence / 14 Sep 2026 / 6 min read

Measure Embedding Anisotropy Before Trusting Cosine Similarity

Cosine similarity is often treated as if a score has the same meaning across any embedding space. That assumption breaks when vectors occupy a narrow region of the available geometry. If many embeddings share a strong common direction, unrelated items can receive positive cosine scores simply because both align with that direction. This behavior is usually described as embedding anisotropy. It is not a defect in cosine similarity itself. The issue is that cosine measures angles in the representation it receives, including global structure that may have little value for the downstream comparison.

Artificial Intelligence Embeddings

Cybersecurity / 14 Sep 2026 / 6 min read

HTTP Request Smuggling Exploits Parser Disagreement

HTTP Request Smuggling Exploits Parser Disagreement A reverse proxy and an application server can each parse the same byte stream according to rules that appear reasonable in isolation. Trouble starts when they reach different answers about where one request ends. Bytes treated as the tail of a request by the front end can become the start of another request at the back end, shifting the interpretation of traffic that follows on a reused connection.

Cybersecurity HTTP

Cybersecurity / 14 Sep 2026 / 7 min read

HTTP Request Framing Must Agree Across Every Hop

A reverse proxy can accept a byte sequence as one HTTP request while the application server behind it interprets part of the same sequence as the start of another. Neither component needs to contain a memory-safety defect. The security failure sits in the disagreement between their parsers. This is the central condition behind HTTP request smuggling. Modern web traffic commonly crosses several HTTP-speaking components before reaching application code: CDNs, load balancers, API gateways, service meshes, reverse proxies, and origin servers. Each hop has to determine where one request ends and the next begins. If two adjacent components derive different boundaries from the same traffic, bytes assigned to one request at the front end can acquire a different meaning downstream.

Cybersecurity Web Security

Cybersecurity / 14 Sep 2026 / 7 min read

HSTS Moves HTTPS Policy Into the User Agent

HSTS Moves HTTPS Policy Into the User Agent An HTTPS site can have a valid certificate, modern TLS settings, and a permanent redirect from HTTP, yet still expose a narrow transport-security gap before that redirect is received. If a browser begins with a plain HTTP request, the server has no opportunity to protect that request until it arrives. An attacker able to alter traffic on that path can interfere before TLS is established.

Cybersecurity HTTPS

Tech / 14 Sep 2026 / 6 min read

HDMI eARC Carries TV Audio Back to Sound Systems

A television often sits at the center of several audio sources. Built-in streaming apps generate sound inside the TV, while game consoles and media players can send both video and audio into its HDMI inputs. An external soundbar or receiver then needs a route for that audio. HDMI Audio Return Channel provides such a route. Its enhanced form, eARC, expands the audio formats and data rates that can travel from the television back to compatible audio equipment.

HDMI eARC