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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7b6c6517562ad9bb06a9f2fef474c2125a473024cca999ff5cd0bc97d42ffdd' 
  AND token = 'fXCsJ3kJkos2CVdbdTUk4ZsmMOc1VpwPsd+aMe1g6Bg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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