SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f3c4b68ddfbc32486d6fc50b78c40a3d634f70677916aebf207f178678b849bd' 
  AND token = 'awszRJt7zDXVT3+ljZ+JYkFjwWJb/SP2GmU6DUiJbTw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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