SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4d994a25d212bb667b0e37a2c29ce8984c82a218d8a5488abbf8ef73fc77f728' 
  AND token = 'wSmqtBWib1SRAW8zWc0pCZand+cLWVT21JdB+WoFET8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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