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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '53b37f6024444df7605582e3c5df299eaef1560268c485a58635ccc23682a3bf' 
  AND token = '502aXwYi6EOhb20pA18uAMHiSSyIiCUDzXPb3BmGg2I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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