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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '78d5e7e5402b20f6bd7ee77d38f983edd1996f7a6e57fd8087bf5bef94a8c51e' 
  AND token = 'Xstlg8upjO9PVIy7CGaMI1PkI2Oig6y55cQjVOE9+cE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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