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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a0708da9f8be5e4b2e4e1ecd17fe24f7b7c1cba5bbf02784e777dc86e4381436' 
  AND token = 'IUaq2nK7ACA+OAh8guA2I5pE5uEhbFu1g2ZTNR7hQGM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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