SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b926c3844abe80ec72483182f792d7889fba15c654b0ddfb4e930b11d53c8bd4' 
  AND token = 'JhtU552tg1K0iayLXZR5VMdh0etmpzQhbYj3WcckPSw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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