SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c814e829dfcb7c07dce8542f509394428bf6bea3594f6a9da3205d4833a7eae4' 
  AND token = '+jQjOGGSgH18DSXS0dwRCcXuOXstglZPIhIUEnC/K1E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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