SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6b4895190a7f64bb3c7fac18e021cc56f94450095d98b1ceff189e927bacd75' 
  AND token = '//bgp1TX3qANBgYwdQkrjS+PzhygMjq9YjSvpL8OAXM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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