SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3fd08104555ede7fa52a64928b5d4890fe4bd1b591be647a29f235f2c1fb8a97' 
  AND token = 'qA9KccmU/H40nhX0fSkGwrFfS9tTlzSFduLWm9Ywdt8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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