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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ac55f67439a24e104e4d620abd6d08d889d3e4d6a1c842df1e89fea636ab9f1' 
  AND token = '5u/YNSBj36AAJM4hqyb9gWCnhSUUvjZMG7hQa7kMAlc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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