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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '799de26e8c16cd70e43800eee2df66e1c732ed1956b0b29995534172015c5d51' 
  AND token = '4UCV59lMt0XBffVRLSZdI+Q0SZd0/bIo8Y3HQiTnWro=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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