SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6a5dc168eb8002db851bdac49036a3591c6a6769ed126390a4bca76e402b3a7' 
  AND token = 'd8o7gevLkxiIsL/u9CKQBRH0mdkz4YhZRLqMwMoVuyQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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