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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2f7aa8c1a7cbc0747ab0226bb642d4c912708b12f75d0ad42da19741fef103d8' 
  AND token = '4PfBBJiTgoMBZ6usVUwbfOJPgp7BJv2u4iM6+QHKShk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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