SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '57ab3596b588ce2f005474b3330b46e8d352c00a4937daf2505e5c27e0813350' 
  AND token = 'x5JDHMVtpE1xZpStU2FtzsbZNskaZA7Xcrsxb7dOAok=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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