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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b917d286d37ceb596d7b63a93620c81dff344b70b0d78c5d092eebf49cb9b37b' 
  AND token = 'hAppfZ1MOqnhdL5cwXA7htbSAg//lMg++7OO/LjDu2U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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