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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'dbfc0e709d3b2357ced124ab9cbe4aa8356ebc4144ef293bff9ec0f401e5c196' 
  AND token = 'P4OOJzYFDWgR2MIkHT//IyLcVnQZZi4SklS1Xrc4DXw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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