SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81b7a10638032ae45e2a224174cbbfb2038d04ced6c6d988157997563a558c38' 
  AND token = 'tlHWgtUrqcFZDYoTU61kp5ZO8NtPWEznhTL44Td3vb4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}