SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f8b50990adcade17b6c704fcdf9edab06d9927430c9e63ab05aec87e5498f08b' 
  AND token = 'Vf8QqTWXejEXjtVGoeuFsycfa7ePo6wjWdcyENlpf94=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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