SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4e799c2c9b395cd17fe2c92988ee825abbca2e352ddb88f2c4e342baaf5b1e13' 
  AND token = 'AmBYChofpMNZo4IsTBChume0pRvcvuKJMKzzT+1uTtc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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