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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3c512d5c6cb43315e92b93e97a4736f0e8f4890db96c08e7d4253b5dab3cd18' 
  AND token = '9YR+hVrdNX+Wb8m3kJEZdHI6Gk7TPj6c9ZXjxcHDs0k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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