SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50e55589d08192ea79590f7fd6a341c4f51d456088d09fa848be9c5872d0ba94' 
  AND token = 'qY8JAL1hPtFW1BdvhbM3lDgZGGm7LzoDJj586/QzHLQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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