SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2c1b03730a8e14a703748eaeed88497814acf553c5fbed84888a44396d5da239' 
  AND token = '/ygOL1b6JHNcpBU5LunFwt82fhlFpdLj1oRFQ8BgOws=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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