SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a0cfc415be313455776d796d816d4106e89b91b98fd812bfb2615137a49b4df' 
  AND token = 'guYU8oD/kVAh2aGHn0wdQF4exXaoI77JrldtAF2ZZ/g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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