SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0a3f7f4fb7a1f988d5c72728fc4417dd67fc7e563f96f89841e31dfc4296a385' 
  AND token = 'HwYwwGX1qpTGyHz48kczHvhfqdvRTnkQ+9Vmg47Ef3s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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