SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a144bfecd72ed6bd742f1d23b5b6b84fb0f1797346bd1a46b546610970361bf9' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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