SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '100199b38d2706a145608a1d81159eff16fbc9467625f47128d5cef3e267063b' 
  AND token = 'A7ZqYhVoB1htc8ginPmnhuQwfTIMutsGgP2ffw/CWkQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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