SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21bf726aa3da1441626821abdfc1a0680e600a0dfb1946d1b4ea304a50a6e140' 
  AND token = 'uYe87YAlwZX1ddXrv5pk+ptv4hZ2duEyYspif2h+WJg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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