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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6887dffaef7a859822ed28898755a8fefc1871026a02799e4d313d0269c9e5ba' 
  AND token = 'cFmyKS87+FiyWrN02POQEECMqbizpp3cIE31zwBvUhs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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