SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '623b4e7e4e1a68409921f07606b56fec6da1ab855d87e19f8f9748cb057a5653' 
  AND token = 'GaH0WqD50tl9dMkreJ7pjzSGlyd86ffPw13WBu5owno=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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