SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51649c83db648937f1904fb89020baa603bc254932f1bc7cad0afd597211818e' 
  AND token = 'P3AppaFp2HCCCM4jivtt3eN4xXlf5860BlcQI5YyGWY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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