SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e503d567fe552271e92038c0be6145664b33b31842b936ffb0dae5f521ff839' 
  AND token = '3O4WZhKICfBNTNG2iHWlu4mKYYnvzEYdvty0Mu159jQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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