SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fdf1462a0fa488092fbfbc47e099891ab0b2b1e3240b99186c7afad302dd9943' 
  AND token = '1NR20BBmdEZNBJLwPNtztGhBTd+n0fQ14HZMP1g6RE4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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