SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ecba5fba7490964c635937e110bc489c4e26a10968e7f286cac4641c343d582' 
  AND token = 'iy5bwKiSIfzke9lVEuEqjCXH+7yR8RWrm/QrcdVBJyk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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