SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15d2de1a9b57362a018e7018c5df0a025cf83f4b35d1e7c493671ffe98a54283' 
  AND token = '8txZUFtlxGQ0ztLgOxvqw4e9iR3FiJT6LBqUAN4/cHs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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