SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7b8cdf9b68831b1f0e464b5df937ec9ed424d89ca17cd1cb9e7ccfdd2de5dab5' 
  AND token = 'H8eJQnRt88+NEAe1d3JSzbLJJxWAqfuCpSHoXjM/oBg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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