SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a183cf3ce0759511f9b96e5db439d0136aaca6e5795c3cfc960d271156a71c35' 
  AND token = '/VktrJBLrt6lzbGnoZ5tJy4rKlyyzSfD4C/bFvarXnQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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