SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '877446039935cfcc7f62ed1c5a66b8f50a71e697b65548997fbf425031abb331' 
  AND token = 'avTRgtQDZnnACLXMhIEiX88yBZyrwFISzSGwOWWKohQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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