SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '542a9fd066084ccd71c3cf463e786035ac340fdae034dc32c0fd2054b811784f' 
  AND token = 'lffeKSu0x9xM7oVOyWuhHPBk7WRAlqyfDrsugldlk5E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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