SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2f5f51261132a2ba29558b01433b9122cebc1623b11fbcbfd110a96662f225a1' 
  AND token = 'nRTrqHAB1BNGgk72MzU8qb5WeAnDTYymqHSsc8ADr0w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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