SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c23a449e6a4145b23806ce39750af72c1fda5480f06487e90a938653c575d903' 
  AND token = 'mJOwon4Ptr4Id852UQKPjcskIjaF5OBhg0V9LygdWG8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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