SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50690759b4bf62cc447e04f4bdec5106787fee13512f51c86ac816ccce2a4c02' 
  AND token = 'xpd4hOLDcTKvOMjlVb2PYPKvTkkdQwDUlf3QfdJnLvg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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