SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '16e8f73102cf2ff2c291c18ebf8ccee79fd6ba66160305f300f32a6e777d836f' 
  AND token = '/bGRkEk3i6iCGjdtrk/ZLDOEdhIZ4o8e+MVitUWAAM4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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