SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3791eafa48572799a4456d87d9585142e9f59683a14cc2234a30b88d6091aa5b' 
  AND token = 'XvB7Ch/Ypq8nHHwVE/0Tkv6sMAUQehKv8ltmfmJh3Ls=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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