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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a26483896011fe93abb38335d17265c9d1b68f459f14aa18a3c3cd51ba62a683' 
  AND token = '6EwZZT9J3XnKXRg14e2OpT95igNaeE59jYJgDiajtPI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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