SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6e1f55d34d69c0e2f300ed58be23133d90ce7ce9f1cf54d70441898381a9f66' 
  AND token = 'C8mz6K9SvrEzJWBUCJEz5ICd/AshsruVGkSJbFZR2xo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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