SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3fe658253ff412ae072485b52c3576762249a08ed12266a093fed77fac68678' 
  AND token = 'rmxpMzsMTQobzp9odIGp2OXAZjMkToG608AdkEgttVo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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