SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a842cc1d671fd71ad53319eb3356a20b671f25597cfc4aa56f5ee84bcdf4bf37' 
  AND token = 'urSTwTOzEq5KvPg0FKFXiIghcQs35VV2CSEqXM3+6VY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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