SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4951309b1acf74efc7db6d022be4d3187499c6dae1c331e5ce36833b9713d8f' 
  AND token = 'c2W1f12fnHxrpje4R5/u1I8z972hj23xdhxsQhpyP40=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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