SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75c406c05fab5b5bc899bef67284a8e1243bdf68e04d43b46ba308b1a6dcae13' 
  AND token = 'AGfU7ze/QBoT7uxF3jv2hNtF+NzPaKuVq8CN2xvIEXw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}