SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a876034131e922048f6fe477fe0bb21ac3377a8fd0a1526f38c7a77a715f73e' 
  AND token = 'CoRzZU/9StXea7hzNsvkjwbWIusXQTdT5pKnW1fPVFE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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