SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4ad139941a21d3a536f6db41f9185f98c38fb6782be7018797c0be599860bc75' 
  AND token = 'j34cl8MazzRR3UTZxUt2N0k7hhTfOed+rgLN8/MPTuE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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