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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8a5ecb13daef54f93d5b5b675c436189a5684370d0bfd96f19dd6644e2c74826' 
  AND token = 'DKbQn0FKI99eJf3c7FvNAb83jzdRG9ct2hMj3Y86SqI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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