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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '900d693cafe6a71f98f8e58812d932ef5cdd42afffaa9680c9997562741758a7' 
  AND token = '9FdLen3X/EFX4FvwhzA2zmLe75TXxzC6bR2kCE0utDE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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