SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1a8846fce07460e0f537c476a138ccd5635748322f5ccc61f345973f0376be2a' 
  AND token = 'MLt3Jgi2l8PMYJmeR0I+6KnXBdZqeaivUxLGK2+9bOY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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