Chapter 194: Thresholds and Blind Spots

At 5:40 a.m., when the phone on the pillow beside him vibrated for the third time, Lin Chen opened his eyes. He had no habit of lingering in bed; he threw back the blanket and sat up at once. The moment his left ankle touched the floor, a dull pain shot through it, like a rusted hinge being forced open. He paused for two seconds, waiting for the spasm to pass, then braced himself on the edge of the bed and stood.

In the bathroom, he splashed cold water over his face. The man in the mirror had bluish-gray shadows under his eyes, but his pupils were clear. He twisted open a pill bottle, shook out two ibuprofen tablets, and swallowed them dry. His stomach was empty, and the pills scraped down his throat with an unpleasant roughness, but they would quiet the alarm bells ringing at the ends of his nerves.

Back at his desk, he flipped open his laptop. The screen lit up with a cold glow, illuminating the hardcover notebook spread across the desk and the photocopies of his mother’s medical records. He had to finish running the peak-traffic stress-test curves before seven. The interception rules that the security team had rolled out in a gray release last night would overlap with the headquarters’ stress-test traffic at ten this morning. If the fault-tolerance model was wrong, the cost of scaling would punch straight through the department’s profit line. Old Chen wanted certainty, not “probably” or “maybe.”

He opened a terminal window and typed in the startup command. The script began reading the log samples captured the night before. The progress bar crept forward. The CPU fan let out a low hum. Lin Chen did not keep staring at the screen. Instead, he turned and packed his bag. In the canvas document pouch, he arranged, in chronological order, his mother’s electromyography request form, her medical insurance card, and her medication records from the past two years. Beside them he stuffed a power bank, a spare Ethernet cable, and a compressed ration bar. When he pulled the zipper shut, the weight settled onto his right shoulder. By reflex, he adjusted his balance so his left foot bore as little weight as possible.

6:05. A prompt popped up in the terminal: "Simulation complete. Time elapsed: 38 min 12 sec."

He pulled up the results chart. At 10:15, the curve spiked sharply, exceeding the preset cost threshold by 11.7%. Lin Chen’s brow tightened. He brought up the underlying logs and compared them line by line. The problem lay in the whitelist logic of the interception rules: an IP range from an overseas proxy pool had been mistakenly classified as “low-frequency normal access,” allowing it to slip past the CAPTCHA barrier. Once the stress-test traffic flooded in, those fish that had slipped through the net would instantly saturate the bandwidth.

He did not hesitate. He created a new Python script and rewrote the IP range validation function, introducing dynamic weight decay. The code was not long, but the routing judgments had to be precise to the millisecond. His fingers moved across the keyboard with steady rhythm. At 6:32, he submitted the patch. In the internal ticketing system, he left a note:

"Whitelist logic contains a proxy-pool penetration vulnerability. Fixed and committed to the dev branch. Please sync the update before the stress test. Attached: revised cost curve."

He closed the laptop, picked up his bag, turned off the light, and went out. The motion-sensor light in the corridor clicked on with his footsteps, then went dark behind him.

The subway station had not yet reached the morning rush. The car was spacious, the air-conditioning turned up high. Gripping the overhead rail, Lin Chen swayed with the train. The numbness in his left foot dulled under the alternating strain of sitting too long and the cold air; he knew it was a sign of poor circulation, but there was no way to deal with it now. He closed his eyes and ran through the day’s route in his head: G1420 arriving at 6:30, pick up his parents, take a taxi to Municipal Third Hospital, register, do the EMG, wait for the report. He had to be back at the office by two in the afternoon to add the ROI calculations to the PPT. Time had been sliced into blocks, and not one of them could spill over.

6:25. The exit of the high-speed rail station. The flow of people was sparse. He stood beneath a sign, scanning the gates. G1420 arrived on time. A few minutes later, Lin Jianguo and Wang Guiying came out dragging that familiar woven sack. His father’s back was slightly hunched, his steps slow; his mother clutched her medical file in one hand, her eyes uncertain in the unfamiliar hall.

“Dad. Mom.” Lin Chen went up to them and took the sack. It was heavy, filled with dried herbs and homemade pickled vegetables.

“We’re here,” Lin Jianguo said with a nod, his voice dry.

“The car’s outside.” Lin Chen turned and led the way. There was no extra small talk. He knew his parents were not used to the rhythm of the city; too many words would only make them more tense.

The taxi headed toward Municipal Third Hospital. The ring road was already beginning to clog with morning traffic. Leaning against the window, Lin Chen’s phone lit up. A message popped up in the work group. The security team had replied:

"Patch merged. Thanks. Morning stress test will proceed under the new rules."

Right after that came a private message from Director Li:

"Old Chen just spoke. Add one more ROI calculation page for Friday’s defense. Need to show the drop in hidden costs brought by the interception rules. You handle it."

Lin Chen replied:

"Received. Will update before 2 p.m."

He turned off the screen and tapped his fingers soundlessly against his knee. ROI was not simple addition and subtraction. The interception rules reduced scaling costs, but they increased front-end latency; latency affected conversion rates, and conversion rates affected revenue. In the PPT, he had to draw that chain of logic clearly, dressing “defense” up as “investment” with data. This was not a technical problem. It was a business problem. He took out his hardcover notebook, wrote down the formulas on a blank page, and broke the variables apart. Outside the window, the cityscape raced backward like stretched film.

7:50. The outpatient hall of Municipal Third Hospital. The smell of disinfectant mixed with the sweat of the crowd and hit him head-on. Lin Chen had his parents sit in the plastic chairs of the waiting area while he went to line up at the self-service machines to get their number and pay the fees. The machine was slow to respond, but he worked through it step by step with patience. After getting the receipt, he returned to his seat and handed the paperwork to his mother.

“Go to the EMG room on the third floor. I’ll wait outside.”

Wang Guiying took the slip and rubbed its edge with her fingers. “Go do your work. You don’t need to stay.”

“It’s fine,” Lin Chen said.

He leaned against the wall and watched his parents step into the elevator. The instant the doors slid shut, he felt a brief sensation of weightlessness. Not fatigue—something more like a taut string suddenly loosening by a millimeter. He knew that string could not be allowed to snap.

The waiting was long and quiet. Now and then a nurse pushed a treatment cart down the corridor, the wheels rubbing against the floor in a dull, regular rhythm. Lin Chen did not scroll through his phone. Leaning against the wall with his eyes closed, he rehearsed the structure of the afternoon’s PPT in his mind. Page one: current situation and risks. Page two: interception plan and cost offset. Page three: ROI calculation and long-term return. The supporting data for every page, he had already run through three times in last night’s simulations. There was no luck involved, only redundancy.

9:40. The elevator doors opened. Wang Guiying and Lin Jianguo came out. His mother looked a little pale, but her steps were still fairly steady.

“It’s done,” she said. “The doctor said the report will be out this afternoon.”

“Good.” Lin Chen steadied her by the arm. “Let’s get something to eat nearby first. Then go back to the guesthouse and rest. I’ll pick up the report this afternoon.”

Lin Jianguo said nothing. He only hitched the woven sack higher on his shoulder.

After settling his parents in, Lin Chen took a taxi back to the office. 11:20. Sitting at his workstation, he opened his laptop. The framework of the ROI page in the PPT was already in place; all that was missing was the last set of comparison data for conversion loss due to latency. He pulled up the internal BI system and extracted the latency-conversion curve from the past three months. He imported the data and generated the chart. The red and blue lines crossed one another on the axes, then finally converged within an acceptable range. He took a screenshot and inserted it into the PPT. Save. Backup.

1:50 p.m. He hit send and posted the updated PPT to the department group chat. Attached note:

"ROI calculation page added. Data source: BI system Q2 report. Please review."

Two minutes later, Director Li replied:

"Received. Logic is clear. Old Chen wants to review the full deck at 3 p.m. Get ready."

Lin Chen replied:

"Understood."

He leaned back in his chair and let out a long breath. The pain in his left foot was beginning to throb again. Looking down, he saw that his ankle had already swollen in a full ring. He opened the drawer, took out an elastic bandage, and wound it tightly around the joint, one layer after another. The movements were practiced and unbroken.

2:45. Conference room. Old Chen sat at the head of the table, flipping through the PPT projected on the screen. Director Li stood beside him. Lin Chen sat to one side, spine straight.

“For the latency caused by the interception rules, you’re calculating a 0.3% bounce rate,” Old Chen said, looking up, his gaze sharp. “But what if during a major promotion the abnormal traffic isn’t bots, but an accidental trigger from our internal stress-testing tools? Can your cost model still hold?”

Lin Chen met his eyes. “The traffic signature of the stress-testing tools is different from that of bots. They carry internal authentication tokens. I added a token verification layer in the V4.1 script. If it’s a false trigger, the system will automatically degrade into read-only mode and won’t trigger scaling. The cost ceiling is locked within 15% of the budget.”

Old Chen stared at him for a few seconds. Then he tapped the tabletop lightly twice with his fingers. “Fine. The logic closes. Present it this way on Friday.”

The meeting ended. Lin Chen packed up his laptop and walked out. The lights in the corridor were a harsh white. He took out his phone. The screen lit up. A new text message, from the testing department of Municipal Third Hospital:

"Family member of Lin Jianguo: your mother’s electromyography report is now available. Please bring the treatment card to the self-service machine on the first floor to print it. Also: the report indicates abnormal nerve conduction velocity. We recommend a follow-up consultation with Neurology as soon as possible."

Lin Chen stared at the screen. His fingertip stopped against the glass.

Abnormal. Follow-up consultation.

The two words were like stones dropping into a schedule that had fit together with seamless precision. He took a deep breath and slipped the phone back into his pocket. He did not stop walking; his pace merely quickened a little.

He needed to go get the report. Then he needed to reschedule everything.

The gears were still turning, but the teeth meshing them together had to be tightened one notch further.