SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6239068d952ab7a579eaa06e4324ae72a3865c59641f2480b0e043541580ce09' 
  AND token = 'gRvyxfKw6nyZxhAn3LTagwA0L/FIWK0w4mlu3iBT3+Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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