SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '28804bde98767703217d087aeb79656bb797ec98a804f73e2dee89fb056316cf' 
  AND token = 'fy0SO/dA10s6r2zKqBXnAiL3Viae5BlJYeTzXLugaIE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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