SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f278fc251021b3fea2e66b90356e4c0869b5caf847f1146bca3ca5090a64d087' 
  AND token = 'wREja/VRDyzuHF+JyePcQGKlW7JQRT4ZPXshZr+RIFc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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