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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51f2a391c1e6e16b2ad1a49ff4215249baef91fdc79d3ef61467539a5f8a62e4' 
  AND token = 'G89EiE1IjCqhOE1hzrylbmRJIzXj0czQIXBXr4+sQUU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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