SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '043b2e2cbc0b5df54cb7234fb693d3a0596c297c4d83c91c8f455940e8be93b7' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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