SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4e8ca826e36a7d42653195173303c8bbe562839a349f146529d77e7a437b207d' 
  AND token = '4q2CsWefC6TAyEJGz76krz3t5kbDYyZk/QwwKijKKRE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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