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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '334298ea123295ba378fc0de841d1eb10292af50a49377848a65ef2d1a4f7b59' 
  AND token = 'fbrZ4NRgIJGbRDc/czmlwevb2aLs/u7c4rQn3QL6GFA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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