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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '1b46e37312f8bec14bb83842aa2040309916a28983e7692fa9356b259444623b' 
  AND token = 'ErKv5NVf+OlaeJntWt7Uij1NFQ68WiGnbbLno0QNHvc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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