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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f3f9e8e4588416f803aef2eb65ea6d894a0b0d82ba6b545a0f7a50d59bc54632' 
  AND token = 'c+EBoS2JcZFsgVEeZpFsLl+rIfbkpIZw5VPBClbZbyw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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