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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55ebbf061f7df4bead2ed5dda225446a0ae4546bdfc065c1111e14da46db9ef3' 
  AND token = '92WqxAxxMSX0UUK+I9++oB4BUig0PQE1sKudFlm2FEc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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