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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd21ce3c5e699e217376ebc2d3f45b1bad70b8b45b867def45aa07eccff8be80a' 
  AND token = '288+VvcslcapLjVAz+zdQq+2DoOpeMwjw91BkNZ0U1o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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