SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3d1763ced2ff046a7451e17315482ec4d9ba02dbe9bb79bb944ea5eedb5c322b' 
  AND token = '3SCedPBQoxeHsuCkDZBOWg9hZbIowGaDEMhjAThSUHE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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