SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ab71cb4bd14fbf56499fee0a467ef8f852f1a360471998b38add90f6294cc554' 
  AND token = 'NwfsOcYvM54t0E2ULSz7rjKY9SHhWYMVuNKTlJrmZ+4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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