SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '50b2ba8fd9b1db4004a293d65bbcc55403e0ffb82902e2a79b544b5424259eaa' 
  AND token = 'uvizFrNjv/8/UOenkJ7BfmrvLo/F1qSz+WhnCH0hsWg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00040

JSON explain

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