SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f102791b4824f10a6ed3a757451fc34930c7b528fc2cde6a4332a8b2c3ec4ed8' 
  AND token = 'nSUl4oQu0h1NSFYVZ5OVlzJjUBng2QAcgYT+ahixDzk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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