SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b9c56103672734575f530527250662e7c098a3450e5a49cbfa8b06373a4feed' 
  AND token = 'qwymvNNqNCXPD/kq9bizdtcJ/7X06fiTtCJnHok6rdc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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