SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7b4c9485442c73f9f305d30107c5c3c91a2a2a26f0c1ce8261d4b9b071f48d42' 
  AND token = 'sxOxhqssn6WNuiRvduh9UQbsIMwBTWOgQGo/Vf+hW20=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}