SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '473947d21c12efff6d2438c99f29e0a260919352d9a0665c1bc16b4e70ed0c8b' 
  AND token = 'reaj0DPZwKjTmxCFZ78tGEClMxqzvIkT5juMJEy9j/w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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