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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b09356a79f0dde3c140b5d861cb748f9429e119d165108d4701c194c3b7cff4d' 
  AND token = 'bf21QcYGulQgJEHe4igb2smacArvaH+YLNXB2KF0mHc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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