SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc1aac9ff8cb17826f6342c196e2a285b0542be11a2ab4855666d01eea4bf410' 
  AND token = 'fNjyw1NHzWv2acuTtaerIcn6tKztPmNt9+gxRzs9k50=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00056

JSON explain

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