SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75bd04bcf96e68588b1315593f7fd820b0a069acd2da31460251b09941d9b982' 
  AND token = 'S/1SmDE4iIAj1LvOqaIQpYrJ3QdSqYbHPPYL6mn/b7E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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