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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9b6245ecd46707914afdd6cb498e121cd3903debf6174e2c183582c7d8de3c44' 
  AND token = '+Wtm6UwjJ6q7fxs3qwJ+r7WWqVSGxjZy3gbj6sM6iJQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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