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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c870c299b978520477b8557efa0224b53d6fb821c5a3d885f3070deb9c945868' 
  AND token = 'KOJQw1JnmIwnVbZcdbCeItxYkbyK4tqxfSEQDcmspCk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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