SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '908a3213fefc2751e0bd87e0af56eabbc62b668147280a833511e27c7443891a' 
  AND token = 'SgzPWQghgNVikODgshz5nh4WFzSBDH8POhgfZZn+lZ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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