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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'dc7a307763d9f3d54b216a3be870b3705c6ad0b8f0d09f2b43e1bef4850e11cd' 
  AND token = 'KW2xAHKOCnWWywj8S+UUtdv5tyBIOgkUQU8kUtbl0Oo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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