SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bf5da1ad85b93f988924c2bdeb3a2353040334141fde43cd92ec620d18b36f82' 
  AND token = '1kjbYAgq2ICMiyEuPmmJ7MUYoHNYGTbqc8NGUbxsTus=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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