SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3952fd7a782514c1be661f7b881fe8f06260986b0507bf02591eefd3a7b501fc' 
  AND token = 'RGfJUbYuzAw5ojghFrfsJr0rqhG+oTTRn6RZesABc/g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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