SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0ff20cf3824256a51cb916828c8fd614f3a1f6f9dbb220af26c54339571c3831' 
  AND token = 'tjvlei4TqZe9HGxhocGxspsqT1qGqVywA9+31vyw2JM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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