SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '592b22fade8523265fa03cd6c1aa2a8699280e266624e42048a2c85317fc0af4' 
  AND token = '3dtNHfT1SCGJ0saJs1LT+Lq5jrJpajxO19UTXhgnT28=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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