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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a4b335490435c20915f46ece209926753fd85fcf435e656a7c9e2a00ad342cbd' 
  AND token = 'h0uVt3N5s6zn2uYz+Osa3TARakUzKJoo+l7pXO5KV9A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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