SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '681501caf663eb8dd193fe46f43de5bb2322b198a4a27cc8df8b6109d57d8423' 
  AND token = 'rwMtF+vvQNBiCGXmiXyZeNI1ACyByZMd9FfwFMEul7Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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