Please identify this 0603 component

[hanakp]

It has 0603 package size, I made photos from all 4 sides. I found it in input stage of a photodetector amplifier (PIN diode transimpedance amplifier). I tried measuring its characteristic with Keithley 6487, but there was negligible current up to 200 V (I didn't want to go higher). It has capacitance of 1.4 pF up to about 30 MHz, then it slowly increases. I think it's polymer ESD protector, or maybe single-layer capacitor. However, I'd like to know exact type, if possible.

Thanks for any tips!

[thm_w]

Input stage where? Surrounding circuitry would be helpful.

The highest 0603 TVS I see is 150V and doesn't look like this, though some other parts do look vaguely similar.
This almost looks like a SRF or something, but, probably not if its open circuit.

[hanakp]

I'm attaching schematic. The unknown component is connected in parallel with the feedback resistor, I triple-checked it. It's an odd place for ESD or other protection component. But there is no reason to use an exotic capacitor either, because the device works only up to 1 MHz or so. Visually, the closest components I could find are these polymer ESD suppressors, but they have solderable terminals only on the bottom, whereas my part also has them on top:

https://cz.rs-online.com/web/p/diody-tvs/1713897

Notice that in my photos, the terminals are rectangular on one side, but have arc cutout on the other side.