SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79dc6e115f917d6023a60935bbc6d56b9091249789d3f8631f50834569f8865b' 
  AND token = '92TPVxtigAuHU9h4lVkQoRuoUJUVNoJFCX8E5xaxHFk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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