SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9f81787a6754c7256d26d4ec0e27361e700903c0ec3f9093ebf65382bc755998' 
  AND token = 'hFDrhuyOxGuI2DeulteaYufemMV0T+IFQ1f+2ZDvxgQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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