SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15e7b3e8bb8fab1a0f2e1525f43b4f47d882e4b2cf49988ff39ceebe307608a4' 
  AND token = 'SMZPYLLJ4cejl/fdnxI4EzuTcvA3OkJk6yHDsjYMsNA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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