SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4df31e4e5f769079138e9e8797895ca1e0d2c4060475b48010aac28d87473175' 
  AND token = 'pNNQrzxEhemP94SMxeMusMMm5y5OQ16zBgjwTtccMrg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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