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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '376919f4c3c75493844f4e45850329b22060d4e80cbcacdd48c8bd65fe0a366c' 
  AND token = 'qBrwwQY8pk5oxrH6tQRquux2I9SffDZ7uwGzWqGnVec=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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