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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc83f4d1a0aba7fa50496b7c1a1acd686d1a1741fe4dbe59f410d5ade5b08a51' 
  AND token = 'F+xTe+bXqidB+DlfFKXosMGh16SupXKRfDsa0cyHiDg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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