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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68d1b91e39aee7ca2858a81dc25037dbf00c66d0c16aab6fc1c2d7078cbeda92' 
  AND token = '7j/P5VBN2ooZT5NsI9f/wYYfIVi+RLsa1KvvMWMV19A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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