SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '592b4ff4650f6b0dbe8446af3936ebf678e7a27e4ba5a7d0bbfec0e12bd2f298' 
  AND token = 'mgAcrh8ME6uHDrB/Yq6OQ7sMWaNWpTJ3zFrU1I2wAWg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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