SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a50bf0f6699475ff84715c898b5a1df02d0d3edc4c3f3728043795cf30d35ec0' 
  AND token = 'qHc1tRcw4WM8f+kX3FhF84s/fg1YYQ6cw4mIsYzacfk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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