SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9fe84534e91554c76fa0c0a38d759a5000287638a019d47194a6bf10e1a51ef2' 
  AND token = 'Q70KcTjqzY9oEds5ZAvez1c1vzqbYhng+IW/u+V9HwY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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