SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51b250b374b57d7446e49d4d9478cb1ca2886e2db9057203b118fc0d952febd7' 
  AND token = 'QpEDYK3SK1xLvFWRqREUg+GfylHG2bje/b2JX/VeOYw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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