SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7a9ad3350698b864e5af9ae94d1c923a9e1fd8800f769017383ca7a3d00098b4' 
  AND token = 'K4ufEBQJDKm4BL+MnAzplNRy2VjnLlbgSI8LH5HWBFY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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