SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b55f01f64b57c6bf585be60e7551096757cf82be5e2ca051d1c4fe4cac321042' 
  AND token = '5pyenX8GUNCBdnjcnBU2m0bcpudiTM3ZAVqBK6UOBGg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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