SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e5bd4d954c37da32a14ff21d38e4a86061ac07004d69e32c75f3f2dc4794f53' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00111

JSON explain

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