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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2fc03e80e08a581a083319082f24d1c423a2ec16100c81a05e67aa3dd31cef5' 
  AND token = 'sJyhJ1Wsf+zZjeJZdjGqOjAHXp4UjCiHD9KlAoNVzwE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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