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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '87f57590941ccd4573671f67cb31baab18edc4ecf8da3aab74c2e7b0529b9ac8' 
  AND token = 'ECKyNC8mtvQ0lK0A5AAI4vKzUbua94+btGwcMjtuuyE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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