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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '138ef9ff293c62e5de82e4de5f70db4dda3fda2e0004b41939c629a2d61c7be5' 
  AND token = 'CF6GLY/oJsQdmIl1FS3O/GG4srW4gSJzMaDnKvEePmE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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