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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '646747092b1bb7444ec7508e8af192de6d08d89e0d07f7c9a3434562926cd27c' 
  AND token = '5+Qj2vn3cMPswO6xX4fLj/iU97TSoWG2vIfXAe1lbF8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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