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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a50bc4b14cd035ba117d89f3cd1952c29a73a19c07941758b123b359b28a3047' 
  AND token = '12xnpLAnSckY5JwZsHrHR8cwmTi8/+ojgjZtMGVobGM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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