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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3d73cf4c0a257fa24026a7b8c1d6e8096a36ba4fd1d2f9d3e8b31b1b0bd2e351' 
  AND token = 'xhDTlMAzYnSNZMlGad5x4DVRxCT3bp+jFOBbdutQlps=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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