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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c78d7fc9eeeeac8c4c9680064a61417cb1c4bdf7d2de1710d0751f7afbfa46ba' 
  AND token = 'QjKKKMvZocuEtkjs32XlKJmro7MUf13uUDIUX7VMrGQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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