SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b016573fbc83dcbadd1cb5f4989f3c175f51d3cb283d415509b6c0819fe42124' 
  AND token = 'n+GiuUTY4dcsfMyg3kVsOMVV5E+8SejJWvNREznj8Hw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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