SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76e69451943594931138f189eec3d5b69d9729580a93eadf3361423b8c48a2a5' 
  AND token = 'h7ek/QqhWhN+qR/c00QOjfZOEHpBZzwlwjbSpttx3vA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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