SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3094a00c7b49847a70fcc125197f3217dc91f68d846f212df904138e0ffa421f' 
  AND token = 'zYdqiLFqHJphdb0FbKtcOw6LBmC4sXvxmyU5v30V0QI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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