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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6b40fed8affe9908f35d39b6146fa1903001a50fe7160fed7e712199f185858' 
  AND token = '3vqZ4kl3reCPSFJ8dKx3y4TncqFB0a9OhDJsrScyiZM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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