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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f933d488b7fa0ae9fcfb20246e7cc9cb49be68f6aecc6e1aad21f6f19e29f284' 
  AND token = 'QoXCaTn/B/+b3YQkgHdedhjDLbeKrKxYJ2SDIhTjc0k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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