SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '394817e1d60e0a122723a1b33b0001356d332d3f303cb09d4ad6111296513df6' 
  AND token = '3shj7eyAo1d2CIBcLRfpYc2TKM7tiURxhiRepxabUzs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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