SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81900a04364b681c24fc2774b0704af26b42d1a4e957baabaa9a5d921dda1d85' 
  AND token = 'Xh5isOk2GRxilrYuG+Cr06x9zOhRRQD5pXpSJd0xKvs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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