SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '639716e35a787f4086f4de8d23c629d9429a12f21f8ceb53914e637d9786454b' 
  AND token = 'nOwVEqmzqIPoBjMZCy50aghJyWvB1M1SjqbNHnufSvE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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