SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ab75cdee2febc9497ba054d947ec4a63d2ca7411bfc517b49db9078eacf1a568' 
  AND token = 'D/BJsVUjWPL2PqGa46xfoq9Im0vmJBb5DWwV9uYNQvY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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