SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'de6d794dc10398b61febf9d94a53c41f2d739a952b0f3acf573d3ded5ed6cf48' 
  AND token = 'Gf1TAah0O+VDjWXZ3M3YEZl/1P+Z1aZlHgzgA5GLjQs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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