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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ec0f653f8b4dc59185d7d8e35a11c25af03fc44c6623d1ae34cc848eb4ae3cad' 
  AND token = 'oZ2+DmBInabPwanFV8l7RRy4k0wPVGvPjL9CGjNE70g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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