SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75891bea5981320ae03e67b47465d5f4f19585536e5f604f5450b507769e8c34' 
  AND token = 'NCkIHF+AJTjyw6GUdylArwdQ7nYrB6wh27z8oyvrNgg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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