SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f298f0557b57cc554a063167becc13755f5f085d74cd460e35540ec7900b1214' 
  AND token = 'zB4mPe95wPD+bDlhDkj6kJOMv+lwibqNnI+Ex4H5eGk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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