SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a108a8f2065e12fecf2d1015f930e42b42297c3cff524c51582c3657a0a7c3c6' 
  AND token = 'am+F+g8nq/HYY2ZXkjiZwNBs+J1JsmjsFcgW7ppY8XE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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