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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '668eeb728ee1c0801581e95caf379d5443875d639148991626b89edd8864bd5d' 
  AND token = 'BS92O6oal4dez0apN+1FxZozCCb10UMxZXWSKS9/VQk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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