SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '975bd4635ccafbb0f5a8bc316cf8c42926fd920da6b2ff43a92d24164a159973' 
  AND token = 'igwHYm63+oPHstQss/0cbGfYAmMwr6YaDwcehUkI+fs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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