SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e3b50eff7096021732df0016cfc7a58fe1acfd080c97b43f89271d7fd6829842' 
  AND token = 'RnTYV66XJHqsroWLEwKetdld8/FsNBjx/NhnxuJ+Z3s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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