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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c1647d3ba9de427a050d7dcfd427bd121ea275bc6cabf4e0b2e8fe81dc1b88d' 
  AND token = 'k8kMVdVRRc7ZW7iiWDU72hYj/fDTX0ChEROwS9+xTr4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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