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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fed21be091b12dcf438455d47f9ab2a78e92909abe317dc9a41457872b3ef9b3' 
  AND token = '6eGShbKuA56SVMMXHF+gtsNN0SdEym8yE51zztxHZ00=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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