SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '345ae3da74f9040054d8c2476ab3e7ac836653902a340efab9e0e971460bdc6a' 
  AND token = 'mrPju09oeiu9Km8xFXgB8rsDGC4vcg+xMQzejsddHag=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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