SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '298a2d6af478107c623706b41892a09e5492f0def4aff70275007c4505a29078' 
  AND token = 'rH3YuZqMX5d+ot07jT/2BBEbzYtJoZIsAUPMSyd16WQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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