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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8a6d4cf8c45b8b3a656baf93ddd8af9a76030cb180b01bd1306e50fa76bd73b5' 
  AND token = 'ZwGD6+kN2tOHABn8bUGS4WzT8NmXcpsftiDyjNEIjUM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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