SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71ad9af231ca768e2741fbe996ed05119db406db695b6db63221a9597f80add5' 
  AND token = 'lpJ9Pel19fz23DeOdZTI5KU2/zSdwfNVj52QBAFDOlU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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