SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '855559ff62d45cc7113bb5b99bb52d96ffadc29058da5bb34c8d0a848d48e3ed' 
  AND token = 'FbnOPqghxidLFzdDBUJUpHgZkvMkZRiyuKjwOGDfTQg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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