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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b1556c014d8fa2e8015b850df423b3ab013ec7ca1600dd5c514c10cedb207301' 
  AND token = 'LhZh0LjQ+mo/Ac+d5NfcBKyUv2rtELVnkKh/ZlZVqs4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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