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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6e38f2341b8604448ee607c8f87b733e5d9bc052be6df6f3ec795a36f5fe78f' 
  AND token = '481p/8ZueLGhlSNEwPW6VCc77gmpsPzwAfptxZiOGJI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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