SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7b21b79d5306458521c8f01b16b8ee30b8d20d426981548949d7c30a97714cc9' 
  AND token = '21XVgxjjoRw6+kLJ3EedGkdZbGztb//fqsIgDgoct+Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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