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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '837e4a2fe5106f86b619f6f39ce26a283ff50325fc5a017b647fedab1ec97f51' 
  AND token = 'xQekua6cebf23GHzmSsKs+gDp3lxYj/UypeYUR73UH0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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