SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '42b2b865dc288f22b143b9e83e7af8f3102f9f351d99e74207c3c735ac69151b' 
  AND token = 'UhHutFMhbfqS3dzcvgmRiT2MeAUVBY3iBZAwtXUy27I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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