SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a21c0f975527168fdd6db93a345481ec0640babf3eaf2248e4588649ecadc367' 
  AND token = 'gZhrWj6cqi+15ny7PgSGJtlXNa6GWwNVHA+THNfmGZI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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