SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15b2b23dcf9d7312e9c15fa64d34135e7450e78c18109857c34f2c856aa75f73' 
  AND token = 'iSRuVtYa1bh6KNzS7FHZiixph8k77520voV5XLhViqU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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