SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d44c92d78cb8996cc170d595b1f572a988366b2cd063d254b88b660b76b210a' 
  AND token = 'elwDo+BWenivQWl61a058478M1SuFYiAe/IaKGT/Jh4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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