SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7a1b313c49a193710d94085a4f4ec85a8e98202a94725e151cc9d0c88a72794' 
  AND token = 'XS4VVRfy8/FwjpBC4ysFeG+0QfVZaHJvquo+j63xoMY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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